| The bilateral-throttle spool valve in the heavy-duty AT shifting control circuit controls not only the engagement and detachment,but also the filling and discharging process of shifting clutches,thus renders its important influence on shifting quality.Most of the work worldwide in the field about dynamic characteristics of spool valves in hydraulic circuits omit the research into the dynamic response of AT shifting control circuit in real working situations,since the factors of working conditions and control signals were not taken into consideration.In this work,the dynamic characteristics of the AT shifting process was obtained through modeling and simulating of the AT shifting control circuit therefore providing foundations for optimizing the structure designing and matching of shifting control circuit and improving the control quality of shifting process.Firstly,the vehicle power transmission system equipped with AT and the working principles of the AT shifting control circuit was introduced.The critical control points and control parameters were proposed through analyzing the AT shifting process,and the significance of studying the dynamic response characteristics of the shifting control circuit was specified.Secondly,the characteristics of fluid passing through the spool valve was studied under Ansys/Fluent,and the simulation results of steady-state fluid force and flow rate were extracted to establish the fluid model of the spool valve.Thirdly,the model of hydraulic control signal and the model of shifting clutches were established,combined with the fluid model,the whole model of the AT shifting control circuit was established in Matlab.The accuracy and the practicability of the model were then verified through results comparison with AMESim simulation and experiment.Lastly,the dynamic response characteristics of the AT shifting control circuit was analyzed using the established model.The impacts of different circuit parameters to the dynamic responses were studied.Given the proper input control signals,the dynamic responses of excessive oil filling condition,insufficient oil filling condition and exact oil filling condition of the control circuit is obtained and analyzed. |
