Structural Optimization Study On Shift Spool Valve Of High-power Automatic Transmission

Due to the unique advantages on vehicle handling convenience,ride comfort and the reliability aspects,high-power hydraulic mechanical automatic transmission(AT)is commonly used on kinds of heavy-duty construction vehicles and armored military vehicles.The shift control circuit,as an essential part of the AT,has a very important influence on the shift quality control by response sensitivity of control signals.First,considering high-power AT as the research object,the shift circuit dynamics modeling and analysis were carried out in order to improve the shift circuit clutch hydraulic response speed.In addition,the shift spool valve structure optimal parameters are calculated by simulation and optimization.Finally,through the analysis of the different shift spool valve,choose the more suitable valve type to make oil pressure of shift clutch response improved,as well as providing the reference for the follow-up design by verifying feasibility of the improved design.The main research contents are as follows:First,it was analyzed of the flow,pressure and dynamic characteristics of the high-power hydraulic automatic transmission shift circuit,and the mathematical models were established,based on the dynamic and flow balance equation.Then The AMESim simulation model was established.Second,the orthogonal test method and design of experiment(DOE)analysis were carried out to explore the influence of the structure parameters of the shift spool valves,which included the spool diameter,stem diameter,spring stiffness,spring pre-compression stroke,the maximum stroke of the valve core,feedback cavity damping hole diameter,pilot control cavity length.After that,the main parameters was optimized design by multi-objective optimization method,genetic algorithm,and the reasonable shift spool valve structure parameters were obtained.Finally,to reduce the lag time of shift clutch charging oil process in response as much as possible,analyzed the spool without notch,with chamfer and with U notches.Through analyzing and solving the changes of the flow area in different notches of shift spool valve,dynamic model of the each notch of shift spool valve was established.The flow field calculation software FLUENT was used to calculate and analyze the flow field in various types of shift spool valve,obtaining equivalent flow coefficient and fluid force on the spool valve of all types of notches under different opening and different pressure difference.Through analyzed the system simulation of the effects of each type of valve notches on the system oil pressure response and experiment verification,Determined the system response speed of the spool with U notches is greater than the other two.This study combined with the means of simulation and test to analyze the difference of the spool without notches,with chamfer and with U notches on the system response.It was seen that the spool with U notches have the fastest response speed and is the best choice of the three as the shift spool valves.