The paper presents examination of the properties of single-acting hydraulic drive for valves of internal combustion (IC) piston engines. In the valve actuation system proposed, a Caterpillar solenoid valve of the HEUI fuel system and a commercial hydraulic actuator were used as the distributor and final control element, respectively. The examination was carried out on a specially prepared model of the valve actuation system under consideration. The influence of various construction parameters of the system on the course of the valve displacement process was examined, with analysing such characteristic parameters of the process as delay in the start of the valve motion measured from the beginning of the current control signal, valve opening and closing times, time of the valve kept open, valve displacement vs. time curve, filling ratio of the area under the valve lift curve, and velocity of the valve hitting its seat. The construction parameters whose impacts were analysed included oil supply pressure, total working space volume, power supply voltage, distributor solenoid force, cross-sections of the distributor supply and overflow gaps, total mass of moving distributor parts, engine valve mass, actuator piston diameter, and valve spring characteristic curve. The necessity of using high supply pressures and high control voltages has been proven. Guidelines for designing engine valve actuation systems of this type have been given. It has been shown that due to low flow capacity, the distributors of the type used are only suitable for the hydraulic actuation of small valves of high-speed IC engines. Evidence has been produced that systems to advance the control signal in relation to the required valve opening instant must be applied to compensate for the valve actuation delay and the limited valve opening velocity. The fact that the valve displacement vs. time curve may be shaped within a relatively wide range has also been pointed out.

This paper describes a research stand and results of experimental research of single-acting hydraulic drive for valves of internal combustion engines. The research stand of the hydraulic valve drive was consisted of: typical valve drive for high-speed internal combustion engine, commercial hydraulic actuator, commercial hydraulic accumulator and electrically controlled hydraulic distributor, which controlled the flow of oil supply to the hydraulic actuator. Rexroth commercial servovalve was used as hydraulic distributor for this valve drive. Components of hydraulic valve drive were mounted to specially designed research sleeve. On this sleeve complete drive, which consisted of a hydraulic cylinder and servovalve, was mounted. Drive control was performed in an open loop with a use of rectangular control signal. Displacement of the valve was measured by an optical displacement sensor. Tests were performed for constant lift of the valve, supply pressure set in the range of 6 to 10 MPa and at fixed temperature of the working medium and different initial deflections of valve spring. The behaviour of the drive was researched for bipolar and a rectangular control signals. Such range of measurements was to determine inter alia: the impact of the supply pressure and the control signals values on the drive work. Obtained results were used to verify the simulation model in a wide range of variation of the characteristic parameters of the electro-hydraulic actuator. The results of experimental measurements like valve movement and pressures in the drive were shown and analysed in this paper. With a reference to the valve movement, a detailed calculations of the valve kinematics were performed. Special attention was given to the opening and closing velocities of the valve, depending on the servo control signal. Subsidence valve velocity during its return movement was calculated. This subsidence valve velocity is an important parameter in terms of the applicability of this drive for the internal combustion engines. Valve opening time delay in opposition to the current control signal was also specified and discussed. Obtained results allowed to conclude that the proposed drive provides acceptable kinematic parameters for high-speed engines at supply pressures of at least 8 to 10 MPa. During the measurements acceptable valve subsidence speeds were obtained. It was found that there is a possibility of adjustment of this parameter by setting the slider servovalve negative overlap. Results became the basis of development of the model of this type of the drive. Further simulation studies will allow to evaluate the applicability of such valve drive for internal combustion engines. Further simulation studies allow to compare the proposed solution with known literature hydraulic valve drives.