Research On Vibration Characteristics Of Hydraulic Poppet Valve Spool

The hydraulic poppet valve is the major control element in the hydraulic system,which consists of valve seat,valve core,spring and controls the quantity of flow,pressure,direction of flow.Moreover,it has been used widely in the hydraulic system,because of its large flow area,good sealing,simple structure and easy operation,and insensitive to hydraulic media.However,it suffered from the influence of fluctuations of oil pressure for a long time,due to the poor stability of the "spool-spring" structure system.With the continuous development of hydraulic technology automation and high precision,the requirements for the performance of the hydraulic poppet valve gradually become higher.Therefore,it is of great significance to study the vibration characteristics of hydraulic poppet valve spools.In this paper,the basic theory of spool vibration is used to analyze the vibration characteristics of the hydraulic poppet valve.On the premise of discussing the compressibility of the oil,the valve port flow equation,the cavity effect and the hydraulic power,the stress of the spool in axial direction and radial direction is analyzed,the differential equation of spool axial movement and the model of spool radial force are established.Aiming at the test method of poppet valve spool vibration,this paper builds a poppet valve hydraulic test bench and establishes a vibration image shooting system based on the shadow camera method.The pressure signal collected by the sensor is analyzed by frequency spectrum,and the pressure pulsation in the hydraulic system is obtained.The main frequency is 174 Hz,and there is a low-frequency pressure pulsation at 28 Hz.For the spool image taken by the high-speed camera,the calibration work is carried out,the spool contour is obtained by processing the spool image,the virtual apex of the spool is obtained by fitting,and the movement curve of the spool is obtained.Conducting the characteristics on axial vibration research on the valve core,the influence of pressure conditions,spring pre-compression and the half-cone angle of the spool on the axial vibration characteristics of the spool are studied.The results show that with the inlet pressure increases,the vibration equilibrium position gradually increases,the amplitude and the pulse factor gradually increase,and the power spectral density at the main frequency of vibration at 174 Hz gradually decreases;as the outlet pressure increases,the vibration equilibrium position gradually decrease,the amplitude and pulse factor first decrease and then increase,the main frequency power spectral density first decreases,then increases and last decreases;with the increase of the spring pre-compression,the vibration balance position gradually decreases,and the amplitude and pulse factor gradually decrease,the power spectrum density of the main frequency gradually decreases;with the increase of the half cone angle of the valve core,the vibration balance position gradually decreases,the amplitude and pulse factor first decrease and then increase,and the power spectrum density of the main frequency gradually decreases.Conducting the characteristics on radial vibration research on the valve core,the influence of a single parameter on the radial front and side vibration characteristics of the valve core is studied.The results show that the amplitude,pulse factor and power spectral density of the radial vibration on the front of the valve core are all smaller than those of the side,but the amplitude,pulse factor and power spectral density of the two have the same changing trend.As the inlet pressure increases,the amplitude and pulse factor gradually increase,and the power spectral density at the main vibration frequency of 28 Hz gradually decreases;with the increase in outlet pressure,the amplitude and pulse factor first decrease and then increase,the main frequency power spectrum density first decreases and then increases;with the increase of the spring precompression,the amplitude and pulse factor gradually decrease,and the main frequency power spectrum density gradually increases;with the increase of the half cone angle of the spool,the amplitude sum pulse factor first decreases and then increases,and the main frequency power spectral density gradually decreases.The thesis has 56 pictures,3 tables,and 78 references.