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What are the core technologies of the gearbox?

What are the core technologies of the gearbox?
Issue Time:2019-11-23

Speaking of gearboxes, many people may not be unfamiliar, but when it comes to the core technology of the gearbox, most people will think that the gearbox is just a component used in the engine. What core technology can it have? In fact, this is not the case. The gearbox and the engine are all important components of the car chassis power system. Even unceremoniously speaking, the engine without the gearbox is a waste, because there is no gearbox, the engine does not open its fists.


What is the role of the gearbox?

Why can't the engine work after leaving the gearbox? This needs to start with the role of the gearbox. Everyone knows that engines have a milestone in the history of automotive development. Whether it was the invention of the first four-stroke internal combustion engine in 1866, or the current BMW B58 and Nissan variable compression ratio engines, they are constantly challenging the limits of power machinery. However, for several hundred years, the engine has several common problems: first, the engine can not be reversed; second, the range of engine speed changes is small, the torque can not meet the requirements of use; third, once started, the power will be output. . In this case, the gearbox highlights its value. 

Because of the presence of the gearbox, the car achieves the function of reverse gear. Another obvious effect is the ability to interrupt the power transmission of the engine, which is what we often call neutral or idle. The last function, of course, is also the most important function of the gearbox. It is to change the transmission ratio to achieve the purpose of expanding the range of on-wheel speed and on-wheel torque. This allows the engine to work under favorable conditions and can fully play. The performance of the engine, the user's feelings are real and fuel-efficient.


Manual or automatic

When buying a car, the salesperson will usually tell you: This car is a manual gearbox with fun, or it is an automatic gearbox for easy driving. As the name implies, a manual gearbox is a gearbox that relies on the driver to manually shift gears, while an automatic gearbox is a gearbox that automatically shifts gears. Although the manual transmissions are similar, the automatic transmissions are different.

The manual transmission (MT) is very simple. It is mainly composed of gears and shafts. Different gear ratios are used to achieve different gear ratios. It is similar to the mountain bikes we usually ride. It is a manual adjustment gear combination. However, the MT is really a little hard to drive, and the combination of clutch + brake + accelerator pedal has caused many new drivers to suffer. It is the case that many new drivers often encounter manual driving when they are unable to change gears. However, for players who like performance cars, manual gears rely on fast power response, you can drive according to your own ideas, and the advantages of fuel economy make them do not want to stop.

The automatic transmission can be divided into a hydraulic automatic transmission (AT), a mechanical stepless transmission (CVT), and a dual clutch automatic transmission (DCT). Although the automatic transmission exists for the convenience of the user to drive, but because of the power transmission method, design concept, etc., there is still a big difference in the experience. The following is a combination of actual models to specifically talk about the characteristics of different automatic transmissions and the core competitiveness of related manufacturers.


A wide variety of automatic transmissions


Hydraulic automatic transmission (AT)

AT is an early development of automatic transmission, mainly composed of hydraulic torque converter, planetary gear set and hydraulic control system, the most important of which is its torque converter, which is equivalent to replacing the manual transmission. The clutch is then shifted through the multi-plate clutch to achieve shifting through multiple planetary gear sets.


Generally speaking, when people talk about AT, they will add the number of gears in front, such as 4AT, 6AT and so on. In theory, the more the number of AT gears, the more accurate the TCU has to choose, the higher the transmission efficiency of the vehicle, the better the fuel economy and the more fuel-efficient. But at the same time, the higher the gear position, the design requirements, the manufacturing process requirements, and the higher the vehicle weight layout requirements.


However, from the current point of view, many manufacturers have developed and produced 10AT gearboxes, and carried them to their flagship models. For example, the 10AT gearbox jointly developed by GM and Ford is a vertical layout with a maximum torsion of 800N·m. It is currently mounted on the CT6 of Cadillac. Honda's 10AT adopts a horizontal layout and is the first to use the Accord 10 in the overseas version. . Domestically, it was first introduced to the Acura RDX; the 10AT jointly developed by Toyota and Aisin was also carried on the Lexus LS.


In general, although 6AT has won wide acclaim, AT will not stop at 6AT, and the future of AT is still promising. The core of each AT is improving the number of gears. Although the current 10AT is the most advanced technology, who knows if there will be 11AT or 12AT in the future?


Mechanical Infinitely Variable Transmission (CVT)

The structure of the CVT is much simpler than that of the planetary gear set in which the AT is responsible. Except for the torque converter, the rest is mainly a shifting mechanism consisting of two pairs of tapered pulleys combined with a steel belt. Compared with the AT gearbox, because there is no gear, it is smoother during the shifting process, and the power output is smoother and the comfort is better.

Nissan and Honda are loyal fans of CVT. Most of Nissan's models are equipped with CVT gearboxes. Currently, Sylphy and Trent are equipped with a gearbox with internal codename CVT7 W/R. The CVT adopts a new type of steel belt and pulley to realize the CVT field. The maximum gear ratio of 8.7 enables greater torque transfer and better fuel economy. Honda is also equipped with CVT on various models such as the Civic Accord. It is worth mentioning that Honda's CVT adopts Honda's latest 'G-Design Shift' control technology, with wide gear ratio and precise hydraulic control technology. And the new high-strength transmission belt, to meet a variety of driving needs.


The core of CVT is to improve the load capacity and increase the speed ratio. Nissan can be said to have accumulated rich experience in this respect. After all, Loulan's 2.5L self-priming and Scorpio 2.0T variable compression ratio engine are equipped with CVT.


Dual clutch automatic transmission (DCT)

Dual-clutch gearboxes, many car companies directly called DCT, and Volkswagen's dual-clutch gearbox is called DSG, both of which are just different names. Since the DCT is mentioned, the DSG of Volkswagen cannot be avoided. After all, the evaluation of the DSG of the public is uneven.


The core components of the DSG gearbox system include an intelligent electro-hydraulic shift control system, dual clutch, dual input shaft and dual output shaft. The gearbox contains two electronically controlled clutches that are engaged when the gearbox is in operation. When the shift is approached, the gears of the next set of segments are preselected, but at this time the clutches are still in the disengaged state. Because the DSG gearbox uses mechanical gears to transmit power. Therefore, the power transmission efficiency is higher, the response speed is faster, and the acceleration performance is very good because of the function of pre-shifting.


Volkswagen's DSG gearboxes are available in dry double clutches and wet dual clutches. Among them, the dry type is mainly used in models such as the Sagitar LaVida, and the wet type is mounted on models such as the Magotan Passat. After so many years of development and evolution, DSG is not the DSG that everyone spit out. By virtue of its own characteristics and continuous improvement, DSG finally won back the trust of people.


Therefore, the core of DSG is how to control heat well. The wet double clutch is better. The dry heat problem has always been a bottleneck to prevent the further development of DSG. However, it is believed that Volkswagen can come up with a solution that will satisfy consumers.


As for the various DCTs carried by other brands, it is true that no matter which supplier, Schaeffler or Getrag, after years of development and improvement, the quality is relatively reliable. Speaking of the large-scale problem of Volkswagen's DSG is eight or nine years ago, in recent years, everyone has heard about the news of the large-scale problem of double clutch?


I have told you so much, you may ask me, then what do I choose? Use MT to practice, definitely let you become an old driver; if you want a little fun, buy AT; pursue driving pleasure, pursue direct motivation, buy DCT (DSG); just want to be smooth, home, CVT is quite suitable for you. Of course, the most important thing is to go to the 4S shop to test the car. After all, whether the shoes are suitable for you, you have to try to know.


Since we have talked about the gearbox, let me tell you some tips:

How to see the gearbox oil leakage 

Looking at the gearbox leak is easy. Look down at the back of the car and you can see if there is oil leakage at the bottom of the gearbox. If there is oil leakage, the bottom oil will deposit dust and leave a black oil stain. If there is a small amount of oil leakage, you can check the gearbox for oil stains.


What should we do if the gearbox leaks oil? 

If there is a leak in the gearbox, the first step is to determine if it is seeping or leaking oil. Some oil seepages are not persistent, so don't worry if they are no longer serious. You can continue the short-distance driving and find the service station to check the gearbox oil leakage fault.


If the oil spill gearbox is serious, check it out as soon as possible. When there is obvious shifting shock and frustration in the gearbox, it is necessary to check the transmission oil as soon as possible. Otherwise, the long-term use may cause the transmission oil temperature to overheat and the gearbox gears to be poorly lubricated. At the same time, frequent high-speed operation or rapid acceleration will also lead to an increase in the transmission oil temperature and increase the probability of oil leakage in the transmission. The specific solution is to clean the surface of the gearbox with oil stains, and then apply sealant to the oil spill point. If there is a major fault, the transmission case must be disassembled for inspection and maintenance.


Bad consequences of gearbox oil leakage 

Transmission oil is similar to engine oil and is mainly used for lubrication, cleaning, cooling, rust prevention and sealing. When the gearbox is in operation, there will be high temperature and high pressure. If the gearbox oil leaks, the transmission oil leakage will cause insufficient lubrication and accelerate the friction between the gears. Therefore, it is necessary to check whether the gear wear is found when disassembling the gearbox.

The shift gear needs to be replaced depending on its wear. The oil leakage must be repaired. The gearbox is all gears. As long as the gear is running, the gear needs lubrication of the gear oil. When the gear oil leaks, the gear is dry and friction. After long time without lubrication, the gearbox will be basically scrapped, so take time to repair.

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