Research On Improvement Of Maneuverability Of Excavator Control Valve And Design Of Speed Setting System

With the continuous development of the construction machinery industry and the continuous changes in the working environment,higher requirements are put forward on the performance and efficiency of the excavator.Aiming at the problem that the speed setting of excavator's executing agency needs to replace the multi-way valve spool,according to the static mathematical model of pilot valve and multi-way valve,the relationship between the control parameters of the hydraulic control circuit of the executing agency is calculated,and as a basis,by using the electro-hydraulic proportional control technology,the control mode of the hydraulic control pilot of the excavator is replaced by the electronic control pilot.On the basis of the electric control pilot,a set of speed setting system of the executing agency is designed,the system can set the speed of the movement of a single executing agency according to the driver's handling habits and the work environment requirements,but also can set the speed of the composite movement of the two executing agencies,without the need to replace the multi-way valve spool,which improves the reliability and flexibility of the executing agency speed setting.The research object of this thesis is a medium-sized hydraulic excavator,the main research contents are as follows:(1)Through the method of mathematical derivation,the exact formula for calculating the relationship between the contact displacement and the handle steering angle of depressurized pilot valve have been deduced,compared with the existing linear approximation formula,when the handle steering angle is less than 20 degrees,the calculation results of the exact formula and the linear approximation formula are basically equal,however,when the handle steering angle is greater than 20 degrees,the calculation error of the linear approximation formula is getting bigger and bigger.In order to improve the fine tuning control performance of the depressurized pilot valve,the two-paragraphs platen structure of depressurized pilot valve is proposed.The mathematical model is established according to the static characteristics of the depressurized pilot valve,and the relationship between the output pilot pressure and the steering angle of the handle is obtained.(2)The relationship between the output flow of the multi-way valve and the displacement of the spool under different working conditions is obtained by using AMESim simulation,and use them as boundary conditions to analyze the size of the steady-state flow force on the spool when the multi-way valve is working by using Fluent simulation,and then analyze the influencing factors of the steady-state flow force and its influence on the work of multi-way valve.The relationship between the steady-state flow force and spool displacement is calculated,and then establish the static mathematical model of the multi-valve,the relationship between the pilot pressure and the displacement of the multi-way valve spool is obtained.(3)Based on the electronic control pilot system,this thesis introduces the composition,working principle,hardware selection,stepping motor control and software design of speed setting system of the excavator's executing agency,the commissioner can set the speed of the executing agency through the positive and negative buttons and the OK button on the electronic control handle,and to ensure that the work of the executing agency in accordance with the set speed.