The Design And Research On Fully Variable Hydraulic Valve System Of Vehicle Engine

Performance of the engine is largely dependent on its gas exchange. So the main target of the design for the engine intake system is to improve the volumetric efficiency at full load and reduce the pumping loss at part load. A kind of fully variable valve system driven by valve-train cam is designed and developed in this paper, that can realize the continuous variability of the maximum valve lift, the valve opening duration and the valve timing in the range of 0-360 ° crankshaft angle; that can take into account the engine power, fuel economy and emission. The advantage is that you can reduce the intake losses, realize Miller cycle, improve volumetric efficiency and reduce NOx emissions. The paper chooses EQ486 engine as the alteration object.Firstly, according to the structure and principles of the fully variable valve system, based on the guiding ideology that compact structure, small changes, facilitate processing, to determine a reasonable overall design program to redesigned cylinder head structure of EQ486 engine.Secondly, design casing, tappet and hydraulic piston parts. Casing is the assembly base of the system. Rational design of its exterior to fix the cylinder head, tappet and hydraulic piston parts; Reasonable arrangement of its internal space to install control mechanism and design the high and low pressure oil duct, that offer the hydraulic oil flowing space, and good sealing; To design the diameter of tappet and hydraulic piston according to area ratio of tappet and hydraulic piston equal lift ratio of tappet and valve; combination of bypass valve and rational Design of tappet and hydraulic piston parts achieves that the valve open timely and valve-seating velocity is controlled.Thirdly, design the control mechanism which functions as follow:to have high-pressure or release hydraulic depending on the operating conditions of the engine at the appropriate time, to accumulate and release energy and to seal. Rational design and optimization of the control valve according to the working principle of the control valve and the results of rack tension measurement experiments. reasonable design and installation of the check valve parts depending on the open pressure and casing installation space. The design of the accumulator which is to accumulate and release energy can improve the stability of the control mechanism.Fourthly, design of the drive mechanism, which acts as the driving power source of the system. It can drive the tappet parts and drive control mechanism by a fixed axis gear train to achieve speed ratio of camshaft and the rotor shaft. Rational design fixed axis gear train according to the speed ratio, the relative location, dimensions of casing and other factors. To design high-order polynomial cam profile for the intake according to data.