Shifting Process Research Of AT Hydraulic Control System For Heavy Vehicle

Gearbox is an important part in vehicle power train. Automatic transmission can shift automatically on the basis of driver’s intention, in order to overcome frequently shifting, and reduce driving workload, as well as improve the riding comfort. In recent years, AT technology has been used very wide in China, but it is still very weak of domestic independent R&D ability, meanwhile, it is still the starting stage for heavy vehicle AT research, so that there are still many AT problems to be resolved.This paper carries out based on the863project of "Extra Large Power Assembly". Combined with automatic transmission needs, this paper firstly analyzes the basic structure and operating principle of pressure regulating valve, the solenoid valve and energy accumulator in detail. Secondly, this paper builds clutch mechanical model, analyzes the clutch characteristics, discusses these shift quality index of impact, frictional work and shift time, and proposes some improvement methods. Finally, taking SX2300vehicle with an AT for example, this paper builds shift schedule based on three parameters, and discusses the method of calculating shift opportunity under dynamic property situation.Based on the above theoretical analysis, this paper builds the simulation models of pressure regulating valve, the solenoid valve and energy accumulator using AMESim software, analyzes the shift performance influence from electromagnetic force, orifice diameter and spool quality, and discusses the shift quality influence from pressure regulating valve model and energy accumulator model. Knowing from the simulation results, the solenoid valve structure parameters can change the clutch oil pressure trend, but cannot decrease the pressure surge when clutch connection just begins, as well as cannot change the maximum connection pressure. The pressure regulating valve can change main oil pressure, thus change the maximum connection pressure that can meet the different torque demands. The energy accumulator can effectively decrease the pressure surge when clutch connection just begins, so as to excellently improve the shift quality.In order to check the reasonable of shift progress control, this paper builds a test platform for automatic transmission, and confirms the reasonable by clutch oil pressure changing. Firstly, this paper analyzes the clutch oil pressure parameters of main oil pressure, current value, frequency and the duty cycle. This analysis not only can confirm the simulation result, but also can optimize the shift control strategy, so as to get ideal clutch oil pressure curve. Secondly, this paper analyzes the current value influence to high frequency maintain stage. Finally, this paper builds the alternately shift strategy, based on the above test results and other documents.