[Gearbox Technology] With the increasing publicity of major car companies in recent years, dual gearboxes are rapidly being accepted by ordinary consumers. The rapid and large-scale popularization has also fully exposed its shortcomings, especially the low-speed frustration, abnormal noise and poor stability of some gearboxes. So, the problem can’t be avoided?
Even if you are not the owner, it seems that you can easily tell the shortcomings mentioned above when you mention the dual-clutch gearbox, especially the dry dual-clutch gearbox. After everyone has experienced its extremely fast shift speed advantage, it is not difficult that it also has obvious shortcomings. To get the answers to these questions, we must first talk about the basics.
■ What is the gearbox thinking?
For me, the gearbox can be said to be the best partner. The characteristics of low speed, low speed and high torque are revived by the gearbox, which can make the engine release high torque in the low speed range and low torque in the high speed range, so as to meet the different needs of vehicle climbing, traction or fuel economy. All this is the credit of gearbox gear selection, so why does it shift gears?
When the vehicle is running, the gearbox computer will judge the state of the vehicle through the data transmitted by various sensors, and then it will operate. This process is actually quite similar to our human thinking about life in a daze. Put yourself in the position of thinking about the problems and personal status, and then give solutions, and then the process of practice is exactly the same as that of human beings. This is just a series of actions on the gearbox, which are completed in milliseconds.
■ Can the problems of frustration and abnormal sound be avoided?
The development engineer is the person who has the most say in all kinds of situations of dual-clutch gearbox and the methods and means to solve the defects. As it happens, the editorial department just bought a new 7-speed dry-type one, so we consulted its engineer in charge of the development of dual-clutch gearbox on related issues.
■ Not only software, but also hardware optimization can reduce frustration.
From the problems we have collected, it seems that some dry dual-clutch gearboxes have been criticized by many people for shifting at low speed, so where does this feeling come from? Can it be effectively changed only by adjusting the software control strategy?
In fact, there is a similar semi-linkage state in the power transmission process of dual-clutch gearbox, in order to reduce the wear of clutch plates. Therefore, the engineer will combine the clutch pressure plate with the friction plate as soon as possible. At this time, if the difference between the output speed of the engine and the output speed of the transmission is relatively large, there will also be setbacks.
The previous 7-speed dry dual-clutch gearbox with code DQ200 used mechanical control arm and sleeve to squeeze diaphragm deformation. From the structural point of view, its transmission efficiency is higher. After being optimized for hydraulic system, it can better filter vibration, thus further reducing the occurrence of frustration.
In addition, when it comes to low-speed gear shifting, some friends may feel that the performance of the gearbox is slightly different in the same speed range after the "cold car" state and the "hot car". This phenomenon actually does not only appear in the dual-clutch gearbox, but also exists in AT, etc.
In addition to the optimization of these gearboxes mentioned above, the ride comfort of vehicles is actually related to the engine. Its torque response speed is also one of the factors that influence driving experience. At the same time, the powertrain mounting design also affects the driver’s perceived ride comfort to some extent. Therefore, it can be said that the optimization of powertrain ride comfort is a far more complicated project than imagined.
■ Where does the abnormal sound come from?
The sound generated during the operation of the gearbox, or those unpleasant abnormal noises, will drive the user crazy more than frustration, so where is the source of the abnormal noise? How to optimize it?
■ Poor stability of dry dual clutch?
When it comes to dry dual-clutch gearbox, poor stability or prone to thermal protection is also a problem that people give more feedback. Compared with the natural "weakness" of gearbox structure, how do engineers solve this part of the problem in the development process?
In the testing process, the development team conducted a longer related test for congested road conditions, and simulated the extreme conditions that car owners would encounter in their daily driving on roads with severe congestion and long creep. Finally, through the improvement of clutch plate material and control strategy, the gearbox assembly reaches the design goal of 320 thousand km maintenance-free
Full text summary:
At present, in the domestic market, consumers often regard whether to use the dual-clutch gearbox as the standard to judge the technical maturity of a car. However, compared with the wet dual-clutch, the dry dual-clutch gearbox is more prone to overheating in the face of urban congestion and creeping road conditions because its clutch assembly has no oil to dissipate heat. The structural differences make it at a disadvantage in terms of stability. In addition, in the process of its work, the sound generated by the fork and clutch plate also affects the use experience to a certain extent. From the engineer’s point of view, the problem can be solved to some extent by software control strategy. In addition, some problems can be solved at the hardware level by using hydraulic control system and replacing clutch plate materials. (Text/Figure car home Tang Dynasty)