The driving speed of the car is constantly changing, which requires the transmission ratio of the car's transmission to be as large as possible. This is Continuously Variable Transmission (CVT). Although the traditional gear transmission is not ideal, it still occupies the mainstream position of the automotive transmission with its simple structure, high efficiency and great power.
Today, more than 100 years after it has spanned three centuries, the car has not yet used a satisfactory continuously variable transmission. This is the helplessness and imperfection of the car. However, people have never given up their efforts to find an ideal vehicle transmission. Major auto manufacturers have expressed great enthusiasm for the Continuously Variable Transmission (CVT) and have attached great importance to the practical application of CVT in the automotive field. This is a problem that has not yet been fundamentally solved in the world, and it is also the ultimate goal of research in automotive transmissions.
Around the five research directions of automotive gearboxes, auto transmission experts from various countries have launched fierce competitions.
1. Friction drive CVT
The transmission power of the metal belt type continuously variable transmission (VDT-CVT) has been able to meet the practical requirements of cars, and more than 1 million passenger cars equipped with a metal belt type continuously variable transmission have reached. It is reported that the Multitronic CVT, a metal belt type stepless transmission equipped on a large displacement six-cylinder internal combustion engine (2.8L) Audi A6 car, can transmit 142kw (193bhp) power and 280Nm torque. This is a true meaning of CVT.
Another friction drive CVT (named Extroid CVT) is a wheel dial type. Nissan installed it on the XVL concept car for the first time at last year's Tokyo Motor Show. The new Cedric car also uses this CVT. It can be used with a 3L or higher displacement high-power internal combustion engine (engine output of XVL is 330Nm/194kw), which is another important advance in the development of automotive transmissions.
From the V-shaped rubber belt CVT to the V-shaped metal belt CVT to the roller turntable CVT, the research of the friction drive CVT has continued for a whole century, although the development of the friction drive continuously variable transmission has reached a very high level, and it is already equipped. The car has reached a practical level. However, the gear transmission still occupies half of the river, which explains at least four problems:
(1) Continuously Variable Transmission (CVT) is the goal of the automotive gearbox.
(2) Friction drive The CVT is extremely difficult to achieve a high-power continuously variable transmission.
(3) Friction drive CVT transmission is inefficient.
(4) The efficiency of the friction drive CVT, the power cannot be compared with the gear change.
2. Hydraulic transmission
People often confuse the concepts of an automatic transmission (AT) and a continuously variable transmission (CVT). In fact, the two transmissions work completely differently. The hydraulic automatic transmission eliminates the complicated shifting of the manual transmission and the frequent operation of the foot clutch pedal, making driving easy and effortless. However, the hydraulic automatic transmission (AT) is not infinitely variable, and it is an automatic control of step-variable transmission, which does not fundamentally satisfy the requirement of the automobile for the transmission.
From the original rubber belt continuously variable transmission to the modern metal chain stepless transmission, wheel turntable CVT, Centennial revolving Description: stepless transmission is the ultimate attribution of the automotive gearbox, hydraulic automatic transmission is just a transitional product .
3. Electronically controlled automatic transmission
An Automated Mechanical Transmission (AMT) is the same as an automatic transmission (AT). It is not a continuously variable transmission and is an automatic shift control of a step-variable transmission. Its characteristic is that the mechanical transmission part follows the conventional step-variable transmission, but too many control parameters make it difficult to achieve automatic control.
4. Gear Continuously Variable Transmission
Gear Continuously Variable Transmission This is a brand-new design concept that uses a gear drive to achieve a highly efficient, high-power continuously variable transmission.
According to the latest news, a Gear Continuously Variable Transmission (G-CVT) has been successfully trial-produced and several prototype tests have been conducted. The "gearless continuously variable transmission" structure is quite simple. There are less than 20 kinds of non-standard parts and 51 parts, and the production cost is even lower than manual transmission. The loading test is expected this year.
The advantages of gearless continuously variable transmissions are:
(1) Large transmission power, 200KW transmission power is very easy to achieve;
(2) High transmission efficiency, more than 90% of transmission efficiency is easily achieved;
(3) The structure is simple, and the production cost is greatly reduced, which is equivalent to 1/10 of the automatic transmission.
(4) For vehicles, increase transmission efficiency, saving 20%;
(5) The engine works in an ideal state, the fuel is completely burned, the emissions are clean, and the pollution to the environment is greatly reduced.
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