Automobile transmission systems are usually divided into MT manual transmission, AT automatic transmission, DCT(DSG) dual clutch transmission and CVT continuously variable transmission. AT present, there are many brands and models in China automobile market. If you pay attention, you can find a characteristic. Japanese cars especially like CVT transmission, especially Honda and Nissan are almost all CVT models, while Toyota uses CVT for cheap models and AT for expensive models. Of course, Mazda, a maverick, insists on using AT. In the whole Japanese camp, no models use DCT.
On the other hand, German brands are just the opposite of Japanese brands. The main models of Volkswagen and Audi are almost all DSG, while Mercedes-Benz and BMW are somewhat similar to Toyota. The cheap models use DCT, while the expensive ones use AT. For CVT, which is commonly used in Japan, they hardly touch each other. Why is there such a clear dividing line, and why is AT with balanced performance left out?
(Sylphy CVT gearbox)
The most important thing here is the adaptability problem derived from the use environment. CVT gearbox has no gear ratio structure of other gearboxes, so there is no gear shift setback in theory, and the power transmission is very smooth, especially in the case of frequent acceleration and deceleration in urban areas, which is the comfortable big sofa-like driving experience pursued by Japanese cars.
in addition, CVT gearbox can adjust the transmission ratio in real time according to the working conditions of the engine, so that the engine is always in the best operating efficiency range, so CVT is very fuel-efficient in urban areas or at high speeds. However, this fuel-saving advantage can not be reflected when driving at high speed. CVT at high speed needs a lot of oil pressure to clamp the driving/driven wheel and the transmission belt. According to Honda's data, 25% of CVT transmission loss comes from the oil pump that produces high oil pressure.
for the island country of Japan, fuel economy and comfort are more realistic needs, and the speed limit of expressway is also 1km/h, and CVT is the best choice for a large number of urban areas and non-high-speed driving. However, this kind of adaptive demand is just the opposite on German cars. Germany's high-speed unlimited speed, fast speed increase and high-speed fuel saving have become the top priority, so CVT has been ruled out first.
(DSG gearbox)
The DSG(DCT) dual-clutch gearbox can solve this problem very well. On the basis of MT, an automatic gear shifting mechanism and clutch are added to become DSG. The two clutches are closely matched, and the gear shifting speed is faster. The simple structure means higher transmission efficiency, stronger power and lower fuel consumption during high-speed cruising, which is a perfect match with supercharged engines. This feature is just suitable for Germany, which can drag at will.
However, the dual clutch also has a congenital deficiency. The design of the pre-shift gear makes it easy to shift up and difficult to shift down. When shifting down, you have to return the pre-shift gear and re-shift it. When you stop and drive in the urban area, the gearbox keeps returning and re-shifting, and frustration is inevitable.
Then why not use AT gearbox? After all, AT gearbox is mature in technology, stable in performance, better in shifting smoothness than dual clutch, higher in shifting speed and transmission efficiency than CVT, and can bear more torque, but it is abandoned by most Japanese and German models.
(Mercedes-Benz 9AT)
In fact, it is more about cost, because the internal structure of AT gearbox is complex, including hydraulic torque converter, numerous planetary gears, solenoid valves, sensors, etc., and the cost is naturally much higher. In addition, the technical patents of AT gearbox are basically monopolized by big manufacturers such as Aisin and AF. If you want to use these advanced technologies, you will naturally have to pay high patent fees, or invest huge sums of money to bypass the patent new research and development.
(BMW 3 Series Shift Paddle)
Under the restriction of high cost, most of the current AT gearboxes are equipped with higher-priced models. Think of some "stingy" models that cancel the engine compartment sound insulation cotton, hydraulic support rod and hood, and it is simply an extravagant hope to equip the AT gearbox with higher price.
written AT the end: Although AT is more balanced in terms of stability and ride comfort, it is still a bit unaccustomed to the automobile industry in China. First, it is difficult to research and develop due to its complex structure, and a large number of patents are monopolized, which has become a roadblock for development. Second, it is expensive and its practicability in China is not the best. However, CVT and DCT have more distinctive characteristics and larger market capacity, so it is reasonable to become the mainstream.
This article comes from the author of Chejia, car home, and does not represent car home's standpoint.