Before introducing different gearboxes, let’s briefly explain "Why do you need gearboxes? For the internal combustion engine, because the internal combustion engine can only have the best power output and fuel efficiency within a specific speed range, it is necessary to keep the engine speed within a reasonable range through gears with different gear ratios to keep the vehicle at different speeds.
Manual Transmission (manual transmission)
At present, manual gearbox is the simplest and most durable gearbox used in internal combustion engine vehicles, and it also has the best transmission efficiency among all types of gearboxes (transmission efficiency here refers to the efficiency of power transmission process of gearbox itself). The full name of manual gear box is "manual gear box", as the name implies, the driver needs to manually switch gears, and at the same time, the left foot must be used to control the clutch to complete the gear shifting action. Because of this, the shift process of manual gearbox in power output is "power output → power interruption (clutch depressed) → gear shifting → power output (clutch engaged)".
The transmission efficiency of manual gearbox falls between 96% and 98% on average according to different gear designs and gear ratios. Because of its simple structure, the manual gearbox is usually lighter and more durable. More importantly, the manual gearbox needs more concentration in driving, and it can control the gear change at will, and there are many special operating skills, which make the manual gearbox not only have the above advantages, but also have a kind of communication and connection between people and cars, which is regarded as an important part of driving pleasure.
However, it is difficult to operate the manual gearbox with both hands and feet, and the manual gear shifting process will also lead to uneven acceleration dynamics because of power interruption. Although these are only small inconveniences, they are also the reasons for the gradual decrease of manual gearboxes.
Automatic Transmission (automatic transmission)
To be subdivided, the automatic gearbox can also be divided into "automatic", "automatic manual" and "automatic manual". In general, an automatic gearbox uses a "torque converter" instead of a traditional clutch to transmit the power of the engine to the transmission gear. Simply put, the difference between an automatic and an automatic manual transmission is that the automatic has only low-speed gears, and it is impossible to select individual gears. Hand-to-hand integration enables you to select individual gears. However, most of the current automatic gearboxes are equipped with the function of manual gear selection, so it is rarely specified that they are automatic or manual-automatic, but they are collectively referred to as automatic gearboxes. Due to the slip in the operation mode of the torque converter, the transmission efficiency of the early automatic gearbox was only about 86%, but with the continuous improvement of the torque converter and the gears of the automatic gearbox, the transmission efficiency of the current automatic gearbox has reached 86~94%.
What about the "automatic manual gearbox"? Although it is classified as an automatic gearbox, the full name of "automatic manual gearbox" is actually the same as a manual gearbox in structure, except that the clutch is controlled by the gearbox computer, so driving can switch between automatic shift mode and manual shift mode. Among them, the self-manual gearbox can be divided into "single clutch" and "double clutch". The structure of single clutch self-manual is almost the same as that of general manual, but the clutch operation is handled by computer. Dual-clutch manual operation has two sets of clutches to handle odd gears and even gears respectively, so as to increase the shift speed. With the gradual maturity of technology, now almost all the markets are manual with double clutches, and manual with single clutch is quite rare.
The transmission efficiency of self-manual gearbox is basically the same as that of manual gearbox, and the shift speed is extremely fast, so that self-manual gearbox often appears in performance cars and super sports cars. The common advantages of automatic and automatic gearboxes are that they are convenient to operate, and the gearboxes are controlled by computers, which can adjust the operation characteristics of gearboxes according to different modes (Sport, Eco, etc.). Although the shift frustration of the early automatic gearboxes is quite obvious, now the new automatic gearboxes can shift gears to an almost imperceptible degree. As for the common disadvantages of automatic gearbox and manual gearbox, they are complicated structure, large volume, heavy weight and high cost of manufacturing or maintenance.
Continuously variable transmission (CVT)
The English full name of continuously variable transmission is "continuously variable transmission", which literally translates as a gearbox with continuous speed change. When CVT, a transmission mechanism, was introduced into the automobile industry in the early days, it was considered as a quite avant-garde and advanced gearbox. Structurally, CVT uses two sets of universal disks and a steel belt to change the gear ratio, thus achieving the effect of speed change, so there is no so-called "gear" in CVT gearbox. CVT gearbox has the advantages of simple structure, linear and smooth shifting process, and because there is no need to shift gears, it can keep the engine in the most efficient speed range without interruption of power, thus achieving good fuel consumption performance.
Although the excellent fuel consumption is achieved because of the operation mode, the transmission efficiency of CVT gearbox only falls between 75% and 88% according to different designs, and CVT gearbox can’t bear large power output generally, so the models equipped with CVT gearbox often make people feel weak in acceleration. In addition to low transmission efficiency, the excellent fuel consumption of CVT gearbox is usually limited to the middle and low speed environment in urban areas. This is because the gear ratio of Puli disk is limited, which makes it difficult for CVT gearbox to have a very comb gear ratio, resulting in high-speed fuel consumption compared with automatic or manual gearbox. In addition, although the smooth shifting of CVT is regarded as an advantage, for many people, the lack of shifting feeling has also become a defect of CVT gearboxes, so now many CVT gearboxes will have more gear simulation functions, so that gearboxes can create a feeling similar to shifting.
However, with the continuous development of automatic gearbox, the performance of fuel consumption, transmission efficiency and shift smoothness has been equal to or even surpassed that of CVT gearbox, so CVT is already an advantageous technology in the eyes of most car manufacturers. At present, only Japanese automakers including Toyota, Subaru, Honda and Nissan continue to produce CVT gearboxes, and a large part of the reason is that the local car environment in Japan is really suitable for this type of gearbox.
On the whole, with the continuous improvement of automatic gearbox, there have been 8-speed, 9-speed and 10-speed gearboxes, and the efficiency, quality and shifting speed have surpassed CVT and manual gearbox, especially the dual-clutch gearbox, which is basically impeccable in performance except for high cost. Among all kinds of gearboxes mentioned above, CVT still has room for survival in the market because of its advantages in medium and low fuel consumption, but it is precisely because of the comprehensive advantages of automatic gearboxes that the reason for the existence of manual gearboxes is almost only "driving pleasure", so we can expect that there will be fewer and fewer cars equipped with manual gearboxes in the future, and the rise of electric vehicles will have a better chance to make manual gearboxes disappear in the market in the future. Therefore, in addition to letting fans know about the differences in characteristics between gearboxes, I also hope that fans can cherish this rare animal, manual gearboxes, because today, when this automatic gearbox becomes the mainstream, manual gearboxes may soon disappear.