Wet Clutch Control Study Based On The Digital Proportional Relief Valve

Automatic transmission technology represents development trend of transmission which has been developed rapidly in recent years. The speed difference exists in AT gearbox during the shifting process, and improper separation or combination of wet clutch will seriously affect vehicle comfort and shift quality. Therefore, it is of great importance to control reasonably the rule of pressure variation about wet clutch in shifting process. In the paper, the wet clutch oil pressure is controlled efficiently by the digital proportional relief valve for buffering the process of shifting.The PWM digital proportional cone valve is made up of high-speed switching valve and pilot relief valve. The operational principle of digital proportional relief valve used for gear shifting of vehicle is analyzed, and the main valve geometry and static characteristic parameters are calculated. The dynamic and static performances of high-speed switch valve are researched deeply. And the operational principle of signal control system has been analyzed, the generation of the PWM signal and power driver circuit about high-speed switching valve are designed.The mathematic models of pressure control system of wet clutch are built separately, which are simulated by MSC.EASY5software. Meanwhile, the system structure parameters which affect the wet clutch pressure are studied and the more reasonable parameters are determined.The experimental research on the wet clutch pressure control system is carried out efficiently, which determines the best output frequency of the PWM control signal and analyzes the influence on its flow and fluid temperature of the system pressure. From the comparative analysis with the simulation, the results show that the system of wet clutch pressure based on the digital proportional relief valve meets the design requirements of buffering pressure in the vehicle shifting process.