I. Development status Referring to the dual clutch transmission, the first thought is the DCG (Direct Shift Gearbox) technology based on DCT technology. DSG is currently the most commonly used dual-clutch transmission technology and is the first transmission technology to be used in mass production. Volkswagen presented this technology innovation to the world for the first time in Wolfsburg, Germany in 2002. It applied the DSG to the Volkswagen Golf Production Vehicle and achieved productization. By the end of 2007, a variety of DSG-equipped cars had sold more than 1 million vehicles. MT products are still dominant in some regions such as Europe and China. Due to the importance of the European market for the fuel economy and emissions of vehicles, MT's market share in the European market can still reach over 80%. Before 1995, the automatic transmission had only two kinds of AT and CVT. In recent years, AMT and DCT have gradually grown. DCT, in particular, has greatly improved transmission efficiency and shift performance, while also protecting existing manual transmission production equipment. It has reduced development costs to a certain extent, and it has also met With MT's dominant market demand, it is favored by people. According to the comprehensive investigation and analysis of relevant agencies on OEM supporting and after-sales markets, DCT's share in the European transmission market is expected to reach 29% by 2015. In the Asia-Pacific (excluding Japan) market, sales of DCT will also increase rapidly. At that time, the share can reach 13%. Second, composition and working principle At this stage, DCT products generally have dual clutch single-axis output, combined dual-clutch single-axis output and combined dual-clutch two-axis output in several types of structures. Among them, the combined dual clutch two-axis output is the most widely used and most typical structure in the present stage. It adopts the structure of combined double clutch and double shaft transmission power, and the gear shifting system adopts odd and even files, edge-by-side arrangement, and two outputs. Shaft mechanism, the transmission diagram shown in Figure 1. The transmission has six forward gears and one reverse gear. There are two wet clutches 1, 2 arranged side by side. The transmission gears are in odd-numbered gears (1, 3, 5, R) and even gears (2, 4, 6). The gear) is configured separately and is associated with two wet clutches, respectively. The 1, 3, 5, and R gears are coupled together with the clutch 1, while the second, fourth, and sixth gears are coupled to the clutch 2. The output shaft of the clutch 2 is a solid shaft, and the output shaft of the clutch 1 is a hollow shaft that is placed outside the output shaft of the clutch 2, and the two output shafts are concentric. In addition, there are four synchronizers between the gear gears, which are controlled by the hydraulically controlled gear shifting mechanism to perform shifting of the gears, as well as clutch control mechanisms. These are not drawn in 1. Third, the key technology of DCT DCT's design concept has appeared since 1933, but the complicated shift control process is one of the important factors restricting its practical application. In recent years, the gradual maturity of electronic technology has made the DCT technology develop rapidly. There is an overlapping phase of the two clutch torque transmissions in the shifting process, so there is a high requirement for the control of the clutch during the shifting. In order to ensure shift quality and clutch life, clutch timing must be precisely controlled. If the switching time is not controlled properly, it may cause the interlock between the two gears to involve the impact of shifting, causing the drive system to generate a large dynamic load, causing clutch slippage, self-excited vibration, transmission system impact, etc., resulting in friction. The temperature of the sheet rises, resulting in deformation or even ablation, directly affecting the clutch's separation, engagement characteristics and life. When a vehicle equipped with a DCT transmission starts, there are two control strategies to control the start: 1. Following AMT's starting control strategy, the vehicle will automatically hang one gear at the start, that is, only the clutch 1 will participate in starting; 2. In order to make the two clutches have the same service life and ensure quick start and smoothness, both clutches can be made simultaneously. Into the sliding state, take the starting moment to achieve vehicle start. In the starting process, first and second gears are hung at the same time, and then according to different starting conditions and driver’s intentions, After the slip ratio of the device 1 reaches a certain value, one of the clutches is continued to engage with the other clutch according to the starting operation state to start the vehicle. Take 1st gear and 2nd gear as an example to explain: Before the upshift, only the clutch 1 is engaged, the torque is completely transmitted by the clutch 1 , and the clutch 1 and the engine do not slide relative to each other. When the gear is shifted, the clutch 1 is cut off to supply oil and begins to gradually separate. At the same time, the oil circuit of the clutch 2 is turned on, and as the oil pressure continues to increase, the friction plate gap is eliminated until it is compressed. The friction elements in the clutch 1 and the clutch 2 are completely separated and engaged, all require a certain slip grinding process. Therefore, there is an overlap in the work, and there is no interruption of the power and a continuous power shift is achieved. The downshift process is similar to the upshift process. Transmission upshifts are generally carried out on a step-by-step basis, while downshifts may be skipped downshifts, and double-clutch automatic transmissions may also be skipped downshifts in manual control mode. For example: In the transmission, from 6th to 3rd, press the 3rd down button continuously. Since the 6th and 3rd gears are on different clutch shafts, the transmission will directly drop from 6th to 3rd. However, when the 6th gear and the 2nd gear are on the same clutch shaft when the gear is shifted from 6th gear to 2nd gear, the transmission will be lowered to 5th gear by the lift gear control and then directly reduced from 5th gear to 2nd gear. That is, when jumping downshifting, the starting gear and the final gear are controlled by the same clutch, and the gear is controlled by another clutch. The starting gear and the final gear are not controlled by the same clutch. Can directly jump to the stall. Fourth, application prospects DCT is a transmission technology with very high transmission efficiency. It reacts very sensitively and continuously. It provides driving comfort and at the same time saves up to 15% of fuel compared to conventional automatic transmissions. DCT has a wide range of applications, not only for high-torque sports cars, but also for low-end cars with low torque. The core of DCT is manual transmission technology. It combines the advantages of both MT and AT transmissions to ensure the power of the vehicle and improve ride comfort and fuel economy. Compared with AT, DCT has been cost-competitive, and is generally optimistic about the industry, has a broad development prospects. Since China has a large number of MT manufacturing companies, it can make full use of existing production capacity and facilities to develop DCT products without much increase in development costs. Therefore, China has the basis and conditions for the production of DCT products. However, as far as the technological status of China's automobile manufacturing industry, DCT products still have some technical problems to be solved: (1) improving the rapid heat dissipation and durability of the clutch; (2) optimizing the control strategy; (3) processing of key components And reliability; (4) manufacturing cost control. The dual clutch transmission is a technologically innovative transmission system and is the development direction of the future transmission technology. It is believed that with the improvement and improvement of the above several aspects, DCT will gradually come to the market and eventually replace the existing manual transmission. 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