Study On The Shifting Performance And Realiability Of Hydaulic Automated Mechanical Transmission

Vehicular Automatic Transmission can be divided into three types:Automatic Transmission (AT), Automated Mechanical Transmission (AMT) and Continuously Variable Transmission (CVT). AMT has become a kind of transmission that is full of potentiality, due to its high transfer efficiency, low cost and easiness to manufacture.The research on AMT shifting performance is key technology in developing AMT. Shifting performance directly influence the market competition and industrialization of AMT.1 The objective of the dissertationAMT has good market expectation, but during the shifting procedure, the power must be cut off which causes the poor shifting performance than AT and CVT. Only through improving the shifting reliability can the commercial compentence be established . so the virtual important thing is to find the way to improve shifting reliability2 Introduction to AMTThe development of AMT can be devided into three phases: semi-automatic,automatic and intelligent. The two major part of AMT are: the hardware including the mastered object, executor, sensors and TCU; and the software performance the control strategy.3 influence on the shifting performance by control strategyThe core of the AMT system is the control strategy , the principle of the clutch engagement, shifting procedure, the choice of control method and the CAN communication between TCU and ECU can influence the shifting reliability, the AMT of model"ChangAnStar"make right control strategy and make goodperformance.Shifting schedule is the schedule of auto shifting time between two shifts with controlling parameters. It includes economical and dynamical shifting schedule. At present, shifting schedule of two controlling parameters(vehicle speed and opening on throttle) is mainly used. If shifting schedule is not good, shifting will not happen at right time and the working condition of engine will be severe. It will make the sound of engine abnormally and stability badly through the whole shifting procession. Sometimes even flame out.Schedule of clutch engagement is determined by releasing journey of clutch, opening of throttle, shiftings, vehicle speed and loading. The main controlling goals are engaging quantity and engaging speed. The engaging control of clutch is mainly referred to the control of engaging speed. It is divided into three stages: fast, slow, fast. Shifting quality is directly influenced by the second stage. If engaging harder, it will make shifting concussion, even flame out; If engaging more slowly, it will make the friction time longer and reduce its longevity. The main controlling parameters are difference between initiative and passive and torques on both sides. When torques being approximately equal, it is proved by experiments that it can guarantee shifting time and not make concussion through the procession of engagement at the time of difference of rotating speed below some value. Meanwhile, the abrasion of clutch is not severe. Shifting procedure is the procedure through working harmoniously among engine, clutch and transmission. Their cooperation will affect shifting time heavily. In order to decrease the shifting time, the time that is spent on the friction of the clutch should be decreased first. If we intend to increase the time of non-load stage, which helps to minimize the difference of the rotary speed between the driving disc and the driven disc. If weintend to shorten the time of the non-load stage, engage the clutch immediately after the gear change. The clutch can engage in a satisfying period if the new method of controlling the engaging speed of the clutch is realizable. And the time that is spent on synchronizing the gears should also be shortened. It can be realized in the following two ways. The first is to decrease the difference of the driving gear and the driven gear. The second is to increase the shifting force. If realizing the union control between ECU and TCU by CAN bus, AMT has the best control and the best shifting reliability and performance by use of communication strategy between TCU and ECU.4 influence on shifting Reliability by hardwareThe elements in hardware system are the basis of proper functions of AMT. Executors, sensors, electronic components, hydraulic systems have influences on shifting reliability and. performance, the choice of hardware parameters is of vital important to improvement of shifting reliability. After a great deal of calculation and experiments on hardware parameters, appropriate hardwares are selected for AMT equipped in"ChangAnStar".5 conclutionsGenerally to say, through the research on shifting reliability of AMT, Some productions have been received with the process of"ChangAnStar"project, and this will firmly help AMT to go into the market.