Transmission development trend: from less to more to less
At present, one out of every four cars in the world is sold in China, and the dynamics of China's automobile industry, as a major automobile manufacturer and marketer, have influenced the development of the global automobile industry. Due to the increasing pressure on the environment, transportation and energy caused by the increasing number of automobiles, the goal of reducing the fuel consumption of domestic vehicles by 30% and the average fuel consumption of passenger vehicles to 5 liters per 100 kilometers by 2020 is not just talk. In the next 20 to 30 years, the traditional type of internal combustion engine and various types of transmission will continue to be the main force of automobile powertrain. In this context, how to continue to improve the efficiency of traditional power transmission and how to add more electric power and electrification factors to improve the overall efficiency are the major technical topics to be discussed in the CTI forum.
How does electrification better integrate with conventional powertrains? Which transmission schemes will benefit China? How does the hybrid drive further improve the efficiency of the overall drive system? How do start and shift components improve comfort, power and transmission efficiency? Similar topics were more fully discussed at this year's CTI forum. A reporter from China industry news found some answers when he listened to and interviewed freit kuchuk, chairman of the advisory committee of the CTI forum and a professor at the university of technology in renswick, Germany.
The AT and CVT are still the two more adaptable transmissions
The question of which gearbox is better suited to the Chinese market is an old one, but there is something new in professor ferritt kuchuk's answer this year.
From the perspective of market application, the vast majority of passenger cars in China are still mainly concentrated in super-large and medium-sized cities with dense traffic. Prof freit kuchuk believes that automatic transmissions, including the traditional automatic AT, dual clutch DCT, CVT and AMT, are better suited to the Chinese market in terms of fuel consumption and driving safety.
The AMT is based on a manual transmission that automates the operation of the clutch and shift mechanism. According to the driving condition of the vehicle, the controller can open or close the clutch through the hydraulic or electronic actuator, and control the gear. However, because the traction of the car needs to be temporarily interrupted during the shift, the acceleration of the car is discontinuous, which makes the comfort of AMT relatively low. Because of the high demand for comfort in the Chinese auto market, AMT is not suitable for the Chinese market. On the other hand, the AMT has significant advantages in efficiency and fuel economy, making it a worthwhile option for commercial vehicle transmissions.
DCT is an important product for Chinese transmission suppliers, because Chinese related enterprises have very rich experience in r&d and production of manual transmission. As the DCT is very similar to the gearbox of manual transmission, these experiences of Chinese enterprises can be fully used in the development and production of DCT, and the machine tool used for the production of manual transmission can also be used in the production of DCT. For this reason, Chinese transmission companies have been able to independently develop and produce China's own DCT products. But for a few key components, Chinese companies also need supplies from foreign manufacturers.
Both AT and CVT are more complex in structure, more challenging in research and development, and the core technical knowledge required is deeper, especially involving the structure of gear set, hydraulic torque converter, gear shifting device in automatic transmission, and the development of roller and actuator in CVT. Although the DCT has been rising rapidly in the Chinese market in recent years, and the drive efficiency and comfort it brings are also well known, the AT is still more important for medium and high models, because of the high requirements for comfort in this class of vehicles. Precisely in this respect, AT can provide better starting and shifting comfort and starting power performance, which is why AT accounts for a large share of all automatic transmission market in the world. Therefore, professor ferritt kuchuk believes that it is particularly necessary for Chinese transmission companies to continue to increase the research and development of AT technology.
In addition, based on the driving styles of Chinese customers, the traffic conditions in China, and thanks to the rapid development of CVT in the past 10 years, CVT will play a significant role in the Chinese market and continue to gain greater market share, said professor ferritt kuchuk.
4 - gear transmission has shown the old "active transmission" era has come
Many of today's cars, even newer ones, still have a combination of a naturally aspirated engine and a 4-speed automatic transmission. In the future market with increasing pressure on energy saving and emission reduction, can this power transmission combination still play a major role in the market? Professor ferritt kuchuk has this to say.
Conventional, naturally aspirated engines and transmission systems with 4 - to 5-speed transmissions cannot meet today's fuel consumption and carbon dioxide emissions standards. In order to meet the requirements of the law and regulations, if not with hybrid power, the c-class and smaller models, for example, can only be achieved by using a small direct-injection turbocharged engine with a 7 to 9 speed automatic transmission. For larger models such as suvs, hybrid power systems must be used to meet fuel consumption and emissions requirements.
Given the penetration of electrification into all areas of automotive technology, is there a major change in the direction of the automotive transmission, which is the central role of improving fuel economy? Yes, a scheme to integrate one or two motors into a transmission to achieve what is known as an "active transmission" has emerged. In this kind of transmission, contain electric motor, power electronic device, actuator, sensor, controller, can convert electric energy into mechanical energy in the transmission to realize the automobile drive. To achieve "active transmission", the transmission can communicate with all modules in the vehicle, especially with the drive system, chassis system, driver assistance system and on-board infotainment system. The "active transmission" can shift gears according to different optimization objectives of drivability, comfort, power and fuel economy. It can also separate the engine or motor from the transmission system according to driving conditions and close it when appropriate.
Regarding the future development trend of automatic transmission, professor ferritt kuchuk believes that automotive transmission has made great progress in energy saving and emission reduction in the past 15 years. The high gear of automatic transmission has been increased from 4 to 10 speed. At present, a large part of the transmission products have been electrified, that is, in the transmission system through the installation of electric motors to achieve the hybrid function. For transmissions that are not yet electrified, these products have already met the requirements and can be quickly electrified. An electrified transmission certainly provides a much higher transmission efficiency than a conventional transmission, which is a better way to save energy and reduce emissions. In the near future, the number of transmission gears will be reduced through the use of "active transmissions".