Abstract
Three-dimensional numerical simulations were carried out to investigate the flow dynamic behavior and pressure characteristics of a variable force solenoid (VFS) valve used in automatic transmissions. To visualize the dynamic movement of the spool, a moving mesh with dynamic layering meshes for varying boundary conditions was employed. The motional direction, the speed of the spool, and the notch depth of the advance/delay components were taken into account in the modeling of the VFS valve. The VFS valve was characterized by determining the variation in the equivalent orifice area (EOA) with the spool displacement. The pressure sensitivity was found to be precisely controlled by the relation between the depth and the area of the notch in the range of the characteristic length of the valve. The results of Model D, which takes into account both leakage and notches, indicate that there is a linear pressure response in the range of valve overlap and that there are smooth pressure control characteristics in the range of the two notches. Although the effects of magnetic materials were not included, the VFS with a spool was shown to have an unavoidable and unique hysteresis. This hysteresis can be minimized or maintained at low levels by adjusting the relation between the notch depth and the characteristic length. The effects of varying the oil temperature on the pressure sensitivity and the leakage flow rate were also examined.
Keywords: Variable force solenoid valve, Moving mesh with dynamic layering, Spool notch, Pressure sensitivity, Leakage flow, Hysteresis