Analysis On The Stagnation Force Of Spool Valve Core And Development Of Measuring Device

The hydraulic valve is the basic element widely used in the hydraulic system,while in the hydraulic control valve,especially in the directional control valve,the slide valve is the most widely used.Whether the control of spool valve is ideal will directly affect the stability of the actuator and the safety of the whole machine.Therefore,the problem of spool valve blocking has always been a concern in the field of hydraulic technology.There are various factors causing the stagnation of the slide valve.For example,the shape error of the spool,surface roughness,solid particles in the fit clearance and the thermal deformation of the spool.The problem of stagnation caused by the thermal deformation of the valve core,On the one hand,spool deformation due to throttling temperature rise of slide valve.This is very likely to lead to the stagnation of the slide valve.On the other hand,the temperature and deformation of the valve port vary with the oil temperature of the throttle.(The maximum deformation reaches about half of the valve body core clearance.When the valve port is free of flow,the deformation part may be restored to its original appearance.)Therefore,the deformation of the valve port is uncertain and time-sensitive.This makes the thermal deformation of the valve core difficult to detect.Moreover,the deformation of micron level is difficult to measure,and it has become a difficult point in the study of thermal deformation of spool valve.In this paper,numerical simulation is used to study the factors causing the thermal deformation of spool valve.The influence of the number of slot,the opening of the valve port and the pressure difference between the inlet and outlet of the valve on the thermal deformation of the spool valve was studied by using Fluent and Workbench software.The sliding valve model was built with AMESim,and the impact on the hydraulic pressure of the spool bearing end face of the gap size,the eccentricity of the valve core,the size of the throttle groove and the structure of the slot was simulated.It is found that,with the increase of the number of throttling slot,the liquid pressure of the bearing end of the spool decreases;With the increase of the width of the slot,the hydraulic pressure at the bearing end of the spool increases firstly and then decreases;With the increase of the depth of the grooves,the pressure on the bearing end of the spool decreases,and the magnitude of the change is larger and larger.In addition,the number of throttling groove of the wedge-shaped slots influences its performance relatively large,and the U type throttling grooves are relatively less affected.Finally,the clamping force of the spool is derived through the relationship between the hydraulic pressure of the spool bearing end face,the spring stiffness,viscous resistance,steady state hydraulic force and stagnation force.The results show that the maximum thermal deformation of the spool appears at the top of the U shaped slot,and the deformation of the spool caused by the temperature is 106 times the amount of deformation caused by the pressure.The main research contents of this paper are as follows:In chapter one,it explains the research significance and background of the project,introduces the universality of the slip valve phenomenon in the hydraulic system,and expounds the development process of the spool valve and the development status at home and abroad.As a basic element in the hydraulic system,the slide valve has a brief description of the effects of the stagnation on the system and the factors that cause the stagnation of the slide valve.In chapter two,the stagnation of hydraulic valves caused by various factors is common,our common methods are opening the pressure groove on the surface of the valve core and improving the cleanliness of the oil.In spite of this,the hydraulic hysteresis is still accompanied by the whole history of the hydraulic valve.This chapter analyzes this phenomenon from the mechanism of hydraulic stagnation.In chapter three,the phenomenon of stagnation caused by the thermal deformation of the slide valve is more common.We often encounter the system failure caused by the thermal deformation of the valve core in the system.Therefore,this chapter simulates the thermal deformation of the valve.Besides,the influence of the eccentricity of valve spool,the fit clearance of valve body and spool,the size of throttling slot and the throttle groove structure on the front pressure of the valve are simulated in this chapter.In chapter four,it mainly introduces the experimental device design and processing of the stagnation force measurement.The equipment that we need in the experiment is introduced one by one,and the specific operation process of the experiment is introduced in detail.How to form a single variable and multivariate influence factors in the experiment is also described in this chapter.Finally,the present research results are summarized,and the work that needs to be studied in the later period is prospected.