is to transmit power through the way of "separation" and "combination". It is located between the engine and the gearbox, and is responsible for transmitting the engine power to the gearbox and also cutting off the power transmission. The clutch is a necessary transmission component for manual transmission models. Not only can it be used to transmit power to drive the vehicle, it can also allow the manual transmission to perform shift operations after the power is cut off.
But not only manual gearboxes have clutches, automatic gearboxes also need to use clutches to transmit and cut off power. For example, the DSG (DirectShiftGearbox) automatic gearbox commonly used by the Volkswagen brand is a type of DCT (DualClutchTransmission) dual-clutch transmission. This gearbox inherits the main structure of a manual gearbox, but because it has two sets of clutches, And got the name.
Compared with the two automatic transmissions, AT and CVT, the dual-clutch gearbox adopts a design similar to the internal structure of the manual gearbox. Unlike the manual gearbox with a single clutch structure, it uses two sets of clutches. Complete the power transmission of different gears. The TCU (transmission computer) of the dual-clutch gearbox will control the output shafts of the two sets of clutches to be in different gears. When one set of clutches is in a certain gear and is in a combined state to transmit power, the other set of clutches is combined The output shaft will be in a lower or higher gear, and you only need to switch to another set of clutches every time you change gears. The benefits of this design of
are obvious. It will be able to achieve the same high transmission efficiency as a manual gearbox. At the same time, the two sets of clutches can switch very quickly. If the computer judges the working conditions correctly, it can achieve extremely fast shifting speeds. In addition to efficient transmission and extremely short shifting time, the volume and weight of the transmission body are smaller and lighter than traditional automatic transmissions, making it a more compatible type of automatic transmission.
How does the dual-clutch gearbox work?
The dual-clutch gearbox has obvious advantages, but the design of the two sets of clutches also makes its internal structure relatively complex. The built-in two sets of clutches are electronically controlled and driven by the hydraulic system, corresponding to two Set of planetary gear sets. The different input shafts corresponding to the two sets of clutches are concentrically nested. The solid drive shaft drives one set of gears, and the hollow drive shaft drives another set of gears, which is equivalent to integrating two sets of manual gearboxes. In simple terms, one of the dual clutches corresponds to odd gears and the other corresponds to even gears. When the vehicle is driving in a certain gear, its next gear is already in the standby state. Once the current gear is disengaged, it can be engaged immediately. The next gear.
Therefore, its working principle is completely different from AT and CVT automatic transmissions. The dual-clutch transmission is like two people controlling the vehicle's gear switching. When driving normally, a set of clutches is connected to a gear in the gearbox to transmit engine power to the driving wheels. The TCU will cooperate with the ECU to predict the gear shift intention based on data such as speed and speed, and pre-judge another The group clutch is connected to another gear and is in a standby state. When it is necessary to shift gears, the current clutch in charge of transmission is disconnected, while another set of clutches in the standby state are combined to transmit engine power. Therefore, the shift speed is not only faster than the automatic transmission, but even faster than the manual transmission operated by some professional drivers. What are the main types of
dual-clutch gearboxes? Although
inherits basically the same structure, due to cost considerations and in response to different working conditions and usage requirements, mainstream dual-clutch gearboxes are also divided into "dry" And the "wet" two, mainly in the clutch part and the design of heat dissipation, and whether it can adapt to greater power output requirements. So, what is the difference between the "dry" and "wet" dual clutch transmissions?
1, dry dual-clutch gearbox
Dry dual-clutch transmission uses multiple friction plates and a metal diaphragm connected to the input shaft for power transmission. When the friction plates and diaphragms are compressed, power is transmitted, and when they are separated Interrupt the power transmission, which is the same as the manual transmissionThe method is the same. The advantage of using the friction plate for direct contact for transmission is that the power response will be faster, but the disadvantage is that it cannot withstand excessive torque output, so it is usually not used with a powerful engine.
In addition, the heat dissipation part of the dry dual clutch gearbox also has certain problems. Since the two sets of friction plates and the friction part are enclosed in a small space and can only rely on air cooling for heat dissipation, the heat dissipation is much worse than that of manual transmission. Coupled with the lack of a wet dual-clutch gearbox that uses oil to participate in the heat dissipation design, in the case of frequent low gear shifts caused by long-term congested road conditions, it may cause rapid accumulation of heat and rapid increase in clutch temperature, thereby The overheating protection system is triggered to indicate transmission failure.
2, wet double clutch gearbox
The clutch part of wet double clutch transmission is mainly composed of steel diaphragm, friction plate and inner/outer diaphragm. The outer diaphragm of the two sets of clutches is connected with the driving disc on the engine end, and the inner diaphragm It is connected to the output shaft of the gearbox. When the inner/outer diaphragm and friction plate are pressed together under the push of oil pressure, power is input to the gearbox from the engine end. Different from the dry type, each group of clutches in the wet double clutch has multiple groups of friction plates and steel diaphragms, so the actual friction area is larger, which can transmit more torque and better disperse heat. . At the same time, since the friction part of the clutch is enclosed in the oil cavity, the benefit of the transmission oil participating in heat dissipation is that heat dissipation will no longer be a problem.
The wet dual clutch is stronger than the dry dual clutch in terms of torque, and the heat dissipation performance is better, so it can also match the engine with more powerful power output. Therefore, the 1.4T supercharged engine in the Volkswagen family is usually matched with a dry dual-clutch gearbox, while models with a higher torque of 2.0T and above are usually matched with a wet dual-clutch gearbox.
"dry" dual clutch has a simple structure and is therefore more economical, but the failure rate is relatively high compared to the "wet" with a slightly more complex structure. The "wet" is more powerful, although the most basic "dual clutch" principle is the same, but the way to achieve it is far different. What are the advantages and disadvantages of the dual clutch gearbox
Advantages:
1, the dual clutch gearbox inherits the advantages of manual gearboxes and automatic gearboxes, and the two sets of clutches work alternately to achieve extremely fast shifting speeds , When the car speeds up, it is even difficult to detect its shifting action.
2. Due to the direct friction contact method of manual transmission, there is no hydraulic torque converter to exchange for more direct power transmission, so the loss during transmission is smaller, so the power output and fuel consumption performance are also better .
Disadvantages:
1. Conventional dual-clutch gearboxes do not have the hydraulic torque converter of traditional AT automatic gearboxes and cannot manually control the clutch to achieve "semi-linkage". Therefore, they often switch low gears frequently at low speeds, which is easier There is a sense of frustration, just like an unskilled driver operating a manual gear.
2. Due to the use of computer control and hydraulic systems, it needs to rely on ECU and TCU gearbox computers to complete the work. Therefore, compared with manual gearboxes, more electronic control units and hydraulic control systems and pipelines are required, so the relative failure probability Higher, more sensitive to the quality of transmission oil.
For dual-clutch gearboxes, although it inherits the many advantages of manual and automatic gearboxes, its own shortcomings are in fact more significant, mainly concentrated on obvious low-speed setbacks and more prone to problems such as overheating. However, after years of development and upgrades, as well as the ECU/TCU program carefully tuned by the manufacturers and the optimization of the internal structure, today's dual-clutch gearbox has gradually weakened these original problems and has become a safe choice. Gearbox type.
[The picture in this article comes from the Internet]
