Research On The Proportional Control Valves Of The Auxiliary Braking System Of High-speed Or Overloaded Vehicles

The proportional control valves of the auxiliary braking system of the high-speed or overloaded vehicles is the research object in this thesis, on the one hand, the mathematical model and simulation model of the typical proportional solenoid are established, through the simulation, how each key structure parameters on the proportional solenoid influence the control characteristic is analyzed, methods on how to improve the displacement force characteristic of proportional solenoid and increase the electromagnetic thrust are proposed to, a proportional solenoid static performance test system is developed and the proportional solenoid of the proportional control valve is studied by the system. On the other hand, the structure of the proportional control valve is optimized, the mathematical model and simulation model are established, the structural parameters are analysised by simulation research. The effects of the holes on the spool are studied, and how the load flow to influence the outlet pressure is analysised, finally the improved proportional control valve is tested to validate the theoretical results.The main content of each chapter is summarized as following:In chapter 1, the hydraulic retarder and its electrohydraulic assisted braking system of high-speed or overloaded vehicles are overviewed firstly, and then considering braking conditions, the requirements of proportional solenoid and proportonal control valve are put forward.The research significance and the research content are expounded by describeing the research status of proportional solenoid and proportional control valve.In chapter 2, starting from maxwell's equations and according to the typical structure of the proportional solenoid, the mathematical model and ansoft simulation modelof the proportional solenoid are established. Then each key structural parameters of proportional solenoid on its control characteristic of influenceusing are analyzed, and refering to the results of the analysis, the method on how to improve displacement force characteristic of proportional solenoid and how to increase the electromagnetic thrust are put forward through the simulation research.In chapter 3, according to the performance index of the proportional solenoid and refering to the existing proportional solenoid testing systems, a proportional solenoid static performance test system with high degree of automation, simple system structure and high testing precision is developed. The proportional solenoid of the proportional control valve is experimentally researched.In chapter 4, owing to the problems of the original structure, the proportional control valve is improved, the mathematical model and amesim simulation model of the proportional control valve are established, and the key structural parameters of the proportional control valve are analyzed in detail based on simulation. Then the effects of the holes on the spool are studied, and how the load flow to influence the outlet pressure is analysised. Finally, according to the performance index of the proportion control valve, the improved proportional control valve is tested, the results verified analysis and simulation results.In chapter 5, all achievements of the dissertation are summarized and the further research work is put forward.