When you choose an automatic transmission car, are you confused by names such as "automatic transmission, manual transmission, continuously variable transmission, CVT transmission"? What are the advantages and disadvantages of each of them? ?As for which one is your "food", read on!
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The automatic transmission we often refer to generally refers to a hydraulic automatic transmission (hereinafter referred to as AT transmission). The automated manual transmission is also a type of AT transmission, but it mainly adds a manual gear control system. Automatic models equipped with AT gearboxes are also the most common.
Many BMW models are equipped with a combination of electronic shift knob + 8AT. (The picture shows the current BMW 7 Series) Advantages:
1. Mature technology
AT gearbox is the most widely used and most popular gearbox on the market today. Its mature mechanical structure has also been inherited, developed and carried forward by many manufacturers. For example, Mazda's "Chuangchi Blue Sky" technology 6AT gearbox (related reading) is a product of its technological optimization and has a good reputation among users.
2. Good reliability
The traditional hydraulic automatic transmission uses a hydraulic torque converter (or hydraulic coupling, multi-plate clutch, etc.), which can buffer the power impact of the engine, and is matched with a mechanical combination of planetary gears to achieve stable performance. The torque it can withstand is also very high. Even tanks have models using AT gearboxes.
The German Leopard 2A6 tank is also equipped with an AT gearbox, which shows the good reliability of the AT gearbox. (Pictures from the Internet) Disadvantages:
1. Low transmission efficiency and high fuel consumption
Since the engine power needs to be transmitted to the gear set through a hydraulic torque converter (or multi-plate clutch, etc.), part of the engine power will be consumed in vain. Therefore, compared with manual transmissions (including CVT transmissions), AT transmissions will It uses more fuel.
2. Average comfort
Since the AT gearbox still uses a fixed gear set, the vehicle will cause frustration and noise when shifting gears. Although with the development of technology, the shift impact has been greatly optimized, in theory, AT gearboxes are still not as smooth as CVT gearboxes.
3. Complex structure and slightly higher manufacturing cost
AT gearboxes require more mechanical parts, making the overall weight heavier and manufacturing costs higher than other types of gearboxes. It is only because the AT gearbox technology is too mature and its output is huge that it gives us the illusion of being "cheap".
8-speed hydraulic automatic transmission produced by ZF. (Pictures from the Internet)
CVT continuously variable transmission (hereinafter referred to as CVT transmission) is more common in Japanese models (however, Audi was also a loyal supporter of CVT transmission back then). With the development of technology, more and more models (including autonomous models) are beginning to be equipped with this kind of transmission that does not require the driver to control the clutch pedal. (Related article about test driving models equipped with CVT transmission)
Japanese brands such as Nissan prefer to use CVT transmissions. (The picture shows the CVT gearbox equipped with the new X-Trail) Advantages:
1. More fuel efficient and more environmentally friendly
The CVT gearbox can reasonably select the most appropriate transmission ratio based on engine operating conditions, allowing the vehicle to achieve excellent fuel economy at all speeds. The transmission efficiency of many CVT gearboxes can reach between 90-97%. Correspondingly, because the engine can work under optimal working conditions, it emits less harmful gases.
2. Good ride and comfort
The CVT gearbox has no fixed gears, which makes the vehicle's power output continuous and linear when accelerating, without the vibration and noise of the AT gearbox's shifting shock. Especially in stop-and-go traffic in the city, the comfort is very high.
3. Simple structure and low cost
Since the CVT gearbox does not have the more complex planetary gear structures of the AT gearbox, its overall structure is simple and smaller, making it easier to mass-produce and further reduce production costs.
The CVT gearbox has a simple structure, small size and light weight, further reducing production costs. shortcoming:
1. The acceleration feeling is slightly poor and the driving pleasure is lacking.
Although in theory, the CVT gearbox can be controlled by an electronic logic program with the engine to fully mobilize the maximum torque of the engine, making the vehicle's acceleration and deceleration performance significantly better than that of MT and AT gearboxes. However, in actual models equipped with CVT transmissions, more conservative logic methods are often used to protect the transmissions. Therefore, the acceleration performance of civilian CVT transmissions generally on the market is slightly worse than that of AT transmissions.
2. The maximum torque it can withstand is small and the stability is slightly poor.
The CVT gearbox is driven by a chain (or belt, etc.), so when it is subjected to large torque power, the requirements for the transmission chain are relatively stringent (it cannot break, slip, etc.), so early CVT gearboxes cannot be installed on vehicles with greater power. superior. With the upgrade of technology, the current CVT can now withstand a torque of 400N·m, but the physical limit (many models still have problems such as CVT gearbox slippage) and stability are still worse than AT gearboxes.
Although with the advancement of technology, CVT can withstand increasing torque, the reliability of the transmission chain has always been a "stumbling block" limiting the development of CVT.
Summarize:With the development of technology, no matter what kind of gearbox it is, it is constantly improving its shortcomings and improving its performance. For ordinary consumers, these two gearboxes are mainstream and mature enough to meet daily use. There is no problem at all. Choose according to your needs!
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