It is believed that the automatic file is not unfamiliar to each rider. Whether it is an early CVT, a simple AMT, or a technologically mature AT automatic transmission, it has long been a development trend for passenger cars. However, why are the automatic transmissions on trucks still not popular today?
CVT gearbox characteristics and truck missed
CVT gearbox directly translated is the continuous variable transmission, which is what we often say continuously variable gearbox, as the name suggests is that there is no specific gear, operation is similar to the automatic gearbox, but the change in speed ratio is different from the automatic transmission The skipping process of the box is continuous but there is almost no loss of kinetic energy in the middle.
However, the CVT gearbox is driven by a chain (or belt, etc.), so when subjected to high torque power, the requirements of the drive chain are more demanding (no breakage, slipping, etc.). However, the output torque of the truck engine is always a thousand Nm. Exceeds the limit that current CVT transmissions can carry.
AMT gearbox current main trend of commercial vehicles
The AMT gearbox, which is not favored in the field of passenger cars, has enormous potential in the truck sector. At present, the AMT gearbox is the most heavily loaded truck in the country. Why is AMT popular in trucks?
MT transmission full name should be a mechanical automatic transmission. It is a far cry from the well-known automatic transmission. The AMT gearbox is based on a manual transmission equipped with a set of electronic control elements on the gear control mechanism to achieve the purpose of automatic shifting gears. In simple terms, an electronically controlled shift system is added to the traditional manual gearbox instead of manipulating the clutch shifting process.
Compared to the AT gearbox, the AMT gearbox has a simple structure and the power transmission efficiency is above 90%. Because no torque converter is more efficient than AT, the maintenance cost is lower, and the technology is mature, which is also the main reason for the current heavy-duty truck AMT gearbox assembly.
AT gearbox can't be implemented for multiple gears
Hydraulic automatic transmission (AT), hydraulic automatic transmission through the hydraulic transmission and planetary gear combination to achieve automatic transmission, generally by the torque converter, planetary gear mechanism, shift actuator, shift control system , shift control mechanism and other devices. Because the link between the AT gearbox and the engine is realized by the torque converter, the rigid link of the traditional AMT clutch is reduced, and the wear of the transmission components is reduced, and the comfort and the power have unparalleled advantages.
However, because the internal gear structure of the hydraulic automatic transmission AT uses a planetary gear system and the structure is complex, temporarily unable to meet the needs of more than a dozen stalls. The worldâ€™s leading American Allison Automatic Transmission Company has only recently released a 10-speed AT automatic transmission, and has not yet introduced domestically. The number of gears and the cost price constrain the development of AT gearboxes on trucks.
So what are the factors hindering the development of automatic transmissions in heavy trucks in China? Domestic truck user groups can be broadly divided into two groups, retail and fleet. No matter which side, the primary consideration is cost, because currently there are fewer AMT models and relatively few buyers, so the cost can not be due to the output. The rise will be reduced, which will lead to the high prices of domestic AMT models.
Truck operating conditions and payloads are much higher than those of passenger vehicles. There is a high requirement for shift logic. Manual shifts rely on the driverâ€™s experience and technology, and the logic of the automatic transmission on trucks is for the time being. Can not meet the needs of all users.
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