Continuously variable transmission is a kind of automatic transmission.

There are three common types of automobile automatic wave: hydraulic automatic wave (AT), mechanical stepless automatic wave (CVT) and electronically controlled mechanical automatic wave (AMT). AT present, AT is widely used in automobiles, and AT has almost become synonymous with automatic wave.

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. In recent years, 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.

CVT: The transmission belt with variable groove width and ratchet wheel are used for power transmission, that is, when the ratchet wheel changes the groove width, the contact radius between the driving wheel and the driven wheel also changes, and the transmission belt generally adopts rubber belt, metal belt and metal chain. CVT is truly stepless speed change. Its advantages are light weight, small volume and few parts. Compared with AT, CVT has higher working efficiency and lower fuel consumption. However, the disadvantage of CVT is also obvious, that is, the transmission belt is easy to be damaged and cannot bear a large load. It can only be used in low-power and low-torque vehicles with a displacement of about 1 liter, so the automatic gear occupancy rate is below 4%.

AMT: Based on the original mechanical transmission (manual wave), it mainly changes the manual shift control part. That is, under the condition that the overall transmission structure is unchanged, the automation of gear shifting is realized by adding an automatic control system controlled by a microcomputer. So AMT is actually a robot system to complete the clutch operation and gear selection. Because AMT can be modified on the basis of manual wave in production, it has good production inheritance and low investment responsibility, and is easily accepted by manufacturers. The core technology of AMT is microcomputer control, and the electronic technology and quality will directly determine the performance and operation quality of AMT. It is reported that AMT will focus on the localization of automatic wave automobiles in the future.

Differences, advantages and disadvantages between automatic transmission (AT) and continuously variable transmission (CVT)

Many riders think that an ordinary automatic car is a continuously variable car, but they actually confuse the concepts of the two. Although these two cars are similar in driving operation, in fact, the gearbox is completely different. Automatic gearbox for ordinary automatic transmission vehicles, CVT gearbox for stepless vehicles.

Many riders will feel a pause when driving ordinary automatic vehicles, and they will feel a slight frustration when accelerating rapidly. The power connection has a vacuum period caused by gear shifting. In fact, this is not the quality problem of the vehicle, but is determined by the internal structure of the ordinary automatic transmission. While the speed ratio of CVT continuously changes, passengers will not feel the impact of shifting, power transmission is continuous and smooth, driving is more comfortable, and acceleration is faster than that of ordinary automatic transmission. The transmission ratio selection and gear shifting of the so-called automatic transmission are automatic. "Automatic" refers to the shift of all gears of the mechanical transmission by controlling the actuator of the shift system with the help of the signal system reflecting the engine load and vehicle speed. The driver only needs to control the speed by manipulating the accelerator pedal. In fact, the shift action in the driving process is changed from our own manual shift to mechanical or other mechanisms, which reduces the trouble of shifting. However, there is still a feeling of shifting gears, but driving such a car in Linyi city can show its superiority and reduce the trouble of frequent starting and shifting gears.

The automatic transmission was first introduced by Oldsmobile Automobile Company in the United States on 1940, which freed the driver from the tedious operation of constantly stepping on the clutch and moving the gear lever. However, its disadvantage is that the fuel consumption is obviously higher than that of manual gear, and there are phenomena such as power transmission loss and slow response. How to realize continuous speed change without interrupting power output? The only answer is: cancel the gear. What can replace the gear? At first, people chose variable diameter pulley and V-belt, and the effective diameter change of universal pulley realized the continuous change of speed ratio, thus realizing stepless speed change. However, the rubber belt has limited stress and is prone to aging and slipping, so this stepless speed change technology can only be applied to small motorcycles. Twenty years ago, Fantl Nai Company in the Netherlands successfully developed a steel belt type continuously variable transmission, but it is still difficult to solve the problems of steel belt slippage and wear. Later, continuously variable transmission has been the research object of major automobile companies, and it has only made a breakthrough in recent years. With the advantages of fuel saving, continuous power and convenient driving, it has become the new favorite of high-end luxury cars. In addition, the biggest feature of CVT is fuel saving, which abandons the traditional energy-wasting hydraulic transmission device and adopts new technology to improve fuel utilization and reduce unnecessary speed fluctuation during driving, so it saves fuel. Seeing this, many readers will ask, didn't you say there is stepless speed change fare oil? Indeed, it is more expensive to use a continuously variable gearbox than a manual gearbox, but the fuel economy here is comparable to that of an automatic gearbox. CVT gearbox is more fuel-efficient than automatic gearbox because of its advanced internal structure and working principle. According to the relevant data, in 2002, compared with the 5-speed manual transmission, the Mul-titronic transmission equipped with Audi A62.8 only lost 0. 1 second in 100 kilometers acceleration, while the city fuel consumption only increased by 2%.

At present, more and more vehicles in the auto market are equipped with CVT continuously variable gearboxes, such as Nanjing Fiat hatchback Palio and sedan Siena Speedgear, Guangzhou Honda Fit 1.3LCVT, Audi A62.4 and A62.8 and A4 1.8T, etc. For automobile manufacturers, reducing the cost and simplifying the production process are the key motives for developing CVT, which is mainly used to replace the traditional automatic transmission, because the traditional automatic transmission is too complicated and almost as troublesome to manufacture as the engine.