Research For The Characteristics Of Slewing Control Valve On Truck Crane

Truck crane is the essential construction equipment which makes the lifting operation parts installed on general automobile chassis and has the merits of flexible, high speed and fast transfer. The whole hydraulic system of tuck crane comprises upper part and lower part hydraulic systems and the upper part hydraulic system includes lifting, telescoping, luffing and slewing systems. The relative rotary movement between upper part and lower part of the crane is called slewing motion. Recently the slewing hydraulic system of domestic light or medium-tonnage truck crane is mostly using the bypass throttle orifice circuits. And several problems exist when slewing system is working, such as stalling, whipping, high system pressure, great hydraulic impact, and so on. These problems are related to the changing of load, the method of manipulate, the characteristics of the valve ports of the directional control valve and the characteristics of the whole slewing hydraulic system.In this thesis, the 25-ton truck crane is the subject investigated. The characteristics of the slewing hydraulic system of the truck crane are studied through modeling, simulating and testing. The reasons of high system pressure and great hydraulic impact are found out and the improving methods are presented. The research work of this topic has important theoretic and practical significances to the design and development work of the slewing control valve of domestic or other types of truck crane.This thesis comprises five chapters, which are illustrated as follows.In chapter 1, the types of engineering crane, the main production base of it. the present status and developing trend of truck crane are introduced briefly. The main components of slewing hydraulic system of truck crane, the types and features of mostly used directional hydraulic circuits and cushion hydraulic circuits are introduced. Finally the background, research object and research contents of this thesis are pointed out.In chapter 2, the structure and working principle of the slewing control valve in this thesis are analyzed. Then the simulation model of the slewing control valve and the whole slewing hydraulic system is constructed by AMESim. The load parameters of slewing system are achieved by constructing the load model and performing the real-crane experiment. The problem work conditions recur in the simulation model, which verifies the accuracy and availability of the simulation model.In chapter 3, based on the simulation model, the reasons of problem work conditions are analyzed. The advantages and disadvantages of the speed-regulating valve in the outlet orifice of the valve rod are pointed out. Then two improving method aimed at reducing system pressure and reducing hydraulic impact are presented, simulated and tested, respectively.In chapter 4, the test bench of slewing hydraulic system is constructed. The quantitative test of the two improved slewing control valve is performed. By comparing the testing results, the advantages and disadvantages of the two improving method are concluded.In chapter 5, the main research work and achievements of this thesis are summarized. Then some future research suggestions are proposed.