Is there any defect in the dual clutch gearbox?
Objectively speaking, the early dual clutch did have some defects. Although it was invented earlier and applied for a patent in 1940, it has been limited by control technology. It was not until 1980s that it was widely used in super sports cars and racing cars. It was not until 2003 that Borgwarner and Volkswagen installed dual clutch gearboxes on Volkswagen Golf r32 and Audi tt. However, due to the material, cost and control technology at that time, the actual experience of dual-clutch gearbox was not satisfactory. The main reason is that heat and frustration are inevitable. For racing cars or sports cars, the frustration of dual clutch can be regarded as an advantage, with fast shifting speed and excellent driving and control sense. However, for family cars that tend to drive in cities, frequent congestion environment leads to frequent gear shifting, and the heat and frustration during gear shifting are obvious, which reduces comfort and durability. Therefore, it should be clear that the dual clutch has shortcomings in the early days, but now with the improvement of control technology and materials, the control logic of the dual clutch is gradually improving and improving, and the problems of frustration and heat dissipation of the dual clutch are becoming less and less obvious.
Principle of double clutch gearbox
Dual clutch gearbox can be understood as the combination of two sets of manual gearboxes, and the separation and combination of clutch plates are controlled by electronic control to achieve the purpose of buffering shift speed difference and power transmission. Structurally, dual clutch can be divided into two parts: dual clutch module and mechanical shift structure.
The engine power is transmitted to the dual clutch module through the engagement of the internal teeth of the flywheel on the crankshaft and the external teeth of the dual clutch support ring. The driving disc and driven disc of double clutch are combined, separated and semi-connected by hydraulic control. K 1 clutch plate is connected with odd gear, and K clutch plate is connected with even gear. K 1 and k2 respectively transmit power to odd gears and even gears through hollow transmission shafts. The output shaft of the dual clutch is connected to the odd gear and the even gear respectively through the fork and synchronizer to realize power output.
The dual clutch gearbox with this structure can realize relay shifting. When the car is driving in the first gear, the second gear has been closed, waiting for the clutch to switch. When the car is driving in the second gear, the third gear has been closed for switching, and the switching time is only 0.2 seconds, which will not interrupt the power transmission of the engine theoretically.
Causes of low-speed stagnation and fever caused by double clutch
Because the dual clutch adopts two sets of friction plates, the gear position is switched by using the state of semi-linkage, which buffers the speed difference and the semi-linkage is sliding friction. In order to eliminate or avoid setbacks, semi-linkage takes a long time, which will produce friction and fever. Therefore, in order to avoid overheating of the gearbox, it is necessary to minimize the semi-trailer time, which will lead to gear shifting backwards. In addition, although the dual clutch can shift gears by relay when upshifting, the speed is very slow when downshifting, and it is necessary to change the high gear first and then combine the low gear, so the time will be doubled. For example, when the car is driving in the second gear, the gearbox is combined with the third gear in advance to wait for switching, but when it suddenly encounters extreme acceleration, the tcu of the gearbox detects that the current torque output is not enough and needs to be downshifted, so it needs to be shifted to the third gear first. It takes a long time to enter the first gear, and at this time, the engine speed is increased, resulting in a low gear when the engine speed is high, which is also an insurmountable phenomenon of low-speed acceleration of the dual-clutch gearbox.
Due to the limitation of dual clutch structure, the only way to reduce retrogression is to extend the semi-connecting rod and delay the upshift. Although this will be smoother, fuel consumption and dynamic response will be affected. Fortunately, with the improvement of gearbox heat dissipation technology and high temperature resistant materials, there is no heat dissipation problem at present.
Why do people prefer dual clutch?
Volkswagen's adoption of dual clutch is also helpless. At present, all major car companies in the world have their own gearbox production lines, such as Toyota owning Aisin, Honda's self-developed gearbox, Nissan owning edin dzeko and Mercedes-Benz's self-developed gearbox, BMW ZF and Volkswagen have never owned their own gearbox production lines, and they have never been able to improve their own product lines. However, the patent barrier of AT gearbox has been formed, and cvt gearbox does not meet the positioning of mass products. Therefore, it is not surprising that Volkswagen adopts dual clutch.
Why do domestic car companies also prefer dual clutch?
In the early days, domestic car companies were deeply influenced by the patent barrier of At gearbox and did not have their own gearbox production line at all. At that time, the imported high-end AT gearbox was not assembled for domestic cars at all. Because domestic car companies have their own manual gearbox production lines, the tail structure of dual-clutch gearbox is similar to that of manual gearbox, and it can be produced with a little modification, while international companies such as Borgwarner and Gertrak can provide dual-clutch control modules, so it is normal for domestic car companies to choose dual-clutch.
Can I buy a dual clutch gearbox?
Dual clutch gearbox can be purchased, but wet dual clutch should be purchased as much as possible, and vertical dual clutch is preferred. Due to the circulating heat dissipation and protection of transmission oil, the wet dual clutch allows the friction plates of the dual clutch to buffer for a longer semi-linkage time, thus reducing the probability of wear and frustration. The dual clutch of unity layout is not limited by space and has low requirements for heat dissipation.
Dry dual clutch can only rely on air convection to dissipate heat, which will lead to high temperature of gears that are often blocked by traffic.