Research On Closed Hydraulic Centralized Charging System Of Large Crawler Crane

With more and more widely used of the closed hydraulic system in the construction crane industry,it has been gradually become a development trend,the key technologies of the closed hydraulic system are also becoming increasingly important.For large crawler cranes,a fully-closed hydraulic system is generally used,and the charge system is often independent,and the centrallied charge system is used.In addition to supplementing system leakage and reducing oil temperature,the charge system is also used as a pilot oil source for displacement control mechanisms of pumps and motor,and brakes,etc.If the displacement of charge pump is too small,the system will not work properly;and if the displacement of charge pump is too large,unnecessary power loss will occur.Therefore,the reasonable setting of the parameters of the charge system is particularly important.At present,the parameter setting of the charge system is often set based on actual engineering calculations,and it is often referenced from the volumetric efficiency and mechanical efficiency without theoretical support.Based on MATLAB and AMESim software,the matching relationship between the displacement of the centralized charge system and the flushing relief valve under different operating conditions,and the influencing factors of the minimum matching displacement are simulated and analyzed.Finally,an intelligent variable centralized charge system is proposed and shown the feasibility of this system by simulation.The main contents are as follows:(1)The principle of the closed hydraulic system of the main hoisting mechanism,the walking mechanism,and the super-lift main luffing mechanism is analyzed,and the single closed hydraulic replenishment system and the centralized replenishment system were compared.(2)The mathematical model of system heating is established by MATLAB according to the pressure-flow characteristics and efficiency characteristics of the pump,motor,and hydraulic valve.(3)The setting values of the minimum displacement of the charge pump under different working pressures,input speeds and system flows are simulated,and the relationship between the minimum displacement of the centralized charge pump and the system working pressure,system input speed,and system flow are obtained.(4)The differences between the quantitative centralized charging system and the variable centralized charging system are compared and analyzed,the energy-saving of the variable centralized charging system are obtained,and the ideas and methods for controlling the variable centralized charging system are proposed.(5)The closed hydraulic system of the main lifting mechanism and the variable centralized charge system are built by using AMESim to simulate the system under different working pressure,input speed,and displacement of the main pump,and dynamic characteristic curve of the low-pressure cavity of system is obtained.(6)Aimed at the advantages of the variable centralized charge system,a specific control method for the displacement of the charge pump system was proposed and verified by the simulation model;the control method was improved through the simulation results,and a better control effect was achieved.