Mathematical model of radial matching clearance of slide valve pair under large temperature range environment

The spool valve pair is simplified into a metal spool-sleeve matching and the interference matching between the valve sleeve and the valve body is regarded as a double-layer cylinder. The heat transfer theory is applied to calculate the inside steady-state temperature field of the spool valve. Based on the thermoelastic theory, considering free expansion, thermal stress, residual stress, assembly stress and hydraulic oil pressure, the calculation formula of the deformation amount of valve spool and valve sleeve is derived. On this basis, the mathematical model of the radial matching clearance of the spool valve with temperature is established. The model shows that the difference in stress state and the variability of parts' elastic modulus with temperature can account for the radial matching clearance variation. Taking an electro- hydraulic directional valve as a calculation example, the variation of temperature field distribution and radial matching clearance with hydraulic oil temperature is calculated. The calculation results show that the temperature distribution in the spool valve pair is similar to the uniform steady-state temperature. The increasing hydraulic oil temperature enlarges the radial matching clearance.