Simulation research of the hydraulic drive for valves of internal combustion engine

This paper describes simulation research of single-acting hydraulic drive for valves of internal combustion engines. The proposed drive was composed of commercial servovalve and typical hydraulic single-acting actuator. Research was performed for the prepared and verified model of this drive. In the paper mainly analysed was the impact of control signals on course of valve lift and its characteristic parameters like: delay of start of valve movement in opposition to the start of the control signal, the time of opening and closing of the valve, the valve lifting time, the course of valve lift, fill factor of the area under the valve lift curve and velocity of the valve subsidence. Special attention was given to the closing movement of the valve. Drive control was limited to step control signal. In the final phase of closing the valve, the control method had to slow down and stop the valve, but without a significant influence on the valve closing phase. During research the fill factor of the area under the valve lift curve was calculated and compared with values obtained for the classic drive with cam. A number of simulations allowed to determine the optimal control signal for the course with deceleration of the valve. Based on simulation studies it was found that comparable fill factors of the area under the valve lift curve for cam drive and analyzed electrohydraulic drive were obtained up to over 4000 rpm speed. Above this speed the factor was significantly smaller for hydraulic drive. For low engine speeds the values of factor were acceptable and amounted to about 0.7. Unfortunately for the valve opening times for engine speed 6000 rpm, tested drive did not provide the full opening of the valve and the fill factor of the area under the valve lift curve was unsatisfactory. In this research, the frequency characteristics of the servovalve published by their manufacturers were used. It demonstrated that because of the delay and response speed of the valve is necessary to use units generating a control signal ahead in relation to the desired moment of opening the valve.