| The hydraulic control system mainly consists of valve control system and pump control system.The throttle loss of valve control system is large and the energy efficiency is low.For example,the throttle loss of control valve in hydraulic excavator accounts for about 40% of the output power of hydraulic pump.Pump control system has the advantages of high energy efficiency and precise control.The technology of pump control symmetrical hydraulic cylinder and pump control motor has been widely used in engineering.However,in the field of pump-controlled asymmetrical cylinder,in order to balance the flow imbalance between the two cavities of the asymmetrical cylinder,the domestic and foreign scholars’ solutions mainly focus on adding auxiliary pumps and valves,which makes the system more complex,reduces the energy efficiency and increases the cost,which seriously restricts the popularization and application of the pump-controlled asymmetrical cylinder technology.The asymmetric hydraulic cylinder is widely used in the electro-hydraulic control loop because of its advantages of large output force and small occupied volume.For example,it can reduce the energy consumption of the asymmetric hydraulic cylinder loop and improve its energy utilization rate,which is of great significance to the energy conservation and emission reduction of construction machinery.This is also the basic starting point of this paper.At the same time,because of its large displacement,high control accuracy,shock resistance,long life,strong self-priming capacity,high efficiency and energy saving,radial piston pump is widely used in the injection molding machine,forging and ship engineering fields.It is important to study the characteristics of asymmetric radial piston pump.Based on professor quan long’s asymmetric flow assignment principle,this paper modified the rkp-ii radial piston pump of MOOG company,and designed a variable displacement triple-flow radial piston pump to realize the direct pumpcontrolled asymmetric hydraulic cylinder technology.In this paper,the new type of radial piston pump has been studied in depth,from the theoretical calculation,finite element analysis,simulation modeling to simulation operation,and compared with the traditional radial piston pump,and continue to optimize the structural parameters of the new type of distribution shaft,so that the flow pressure characteristics of the three-flow radial piston pump and the existing pump level.Finally,the new pump is applied to the direct pump-controlled asymmetrical cylinder system to verify the asymmetrical flow distribution characteristics and energy saving effect of the pump.The main work of this paper is as follows:This paper firstly summarizes the research status of pump control system in symmetrical and asymmetric cylinders,introduces the research progress of radial piston pump at home and abroad,and summarizes the existing problems.In view of these problems,the corresponding solutions are proposed,and the main research contents and innovative points of the paper are given.In this paper,the geometric structure and distribution principle of three-flow radial pump are analyzed in detail,and the characteristics of distribution scheme are summarized.According to the internal structure of the radial piston pump with three distribution flow and the movement law of each component,the displacement and flow pulsation formulas of the radial piston pump with three distribution flow are derived through kinematics analysis of the radial piston pump with three distribution flow.The hydrostatic support structure of plunger-slipper assembly and distribution shaft is analyzed emphatically.This paper establishes the finite element model of the new assignment axis by Workbench,analyzes its stress and strain,and compares it with the traditional assignment axis to provide feasibility for the follow-up work.Secondly,through AMESim,the simulation model of variable displacement tandem triple distribution radial piston pump is established.The throttling regulation of the new distribution axis is analyzed,the flow pressure pulsation of the non-dead point transition zone is analyzed,and the optimal structural parameters of the distribution axis are found,so that the pressure flow pulsation can be reduced by about 50%.The radial fluid pressure of the distribution shaft was obtained by simulation coupling,and the feasibility of the new distribution shaft was verified by comparing with the traditional piston pump under the same working condition.The pressure and flow pulsation of the single plunger and the whole pump outlet under different control are simulated and analyzed.In this paper,a system model of three-flow radial piston pump-controlled asymmetrical cylinder is established,and the pressure flow characteristics and energy consumption characteristics of the system and pump under four-quadrant working conditions are analyzed to verify the asymmetrical distribution characteristics and energy saving effect of the pump.The advantages and disadvantages of asymmetric radial piston pump and asymmetric axial piston pump are compared and analyzed.Finally,the main work and conclusion of this dissertation are summarized,and the future research work is prospected. |
