Design And Simulation Of Fully Hydraulic Variable Valve System For Multi Cylinder Gasoline Engine

Based on a certain type of gasoline engine,a fully variable hydraulic valve system(FHVVS,fully hydraulic variable valve system)for a camshaft overhead gasoline engine with a valve rocker is designed in this paper.This mechanism uses a cam to drive the tappet rocker and The hydraulic transmission makes the valve open,reducing the wear of the hydraulic valve system.The instantaneous relative position of the rotor spool and the valve sleeve in the rotor valve mechanism is controlled by a stepper motor,which changes the hydraulic oil drain time,and then changes the valve lift and Valve opening duration.Combined with the exhaust cam phaser provided by the original machine,the three phases of the intake valve opening phase,intake valve lift and valve opening duration can be continuously changed.It has the advantages of stable control system,fast response,cheap price,and small changes to the original structure parameters.This article has done the following design and research for a certain type of gasoline engine FHVVS:(1)Based on the design ideas of stable system,fast response,cheap price,convenient installation,and small changes to the original structural parameters,the overall layout and overall layout of the FHVVS on the cylinder head of the gasoline engine were determined.The working principle of the rotor valve and the working process of the design system based on the principle are introduced in detail;three-dimensional models and two-dimensional drawings of the front and rear housings,hydraulic tappets,hydraulic pistons,inlet check valves,rotor valves,accumulators,idlers and other components have been designed successively,and Explanation of functions.(2)FHVVS uses a cam and hydraulic compound transmission method,and uses high-order function polynomials to fit the intake and exhaust valve lift data of the original machine to understand the basic design parameters of the intake and exhaust valve lift of the original machine;combined with the basic gas distribution of the original machine Parameters and the working characteristics of FHVVS,an intake valve profile suitable for this system is designed,and then the area ratio of hydraulic tappets and pistons and the calculation formula of the overhead valve rocker are used to derive the intake cam profile;Finally,The intake and exhaust cams on a camshaft are phase-designed.(3)According to the design principle of FHVVS,and the structure and model are appropriately simplified,the system is divided into cam and tappet rocker module,hydraulic tappet and piston drive module,valve motion component module,hydraulic pipeline module and control signal module.The relationship between each module and the control signal is combined,and the design parameters of the mechanism are combined,and the simulation calculation model suitable for the system is established by using the AME-Sim software;The theoretical results of the model simulation were verified using the theoretically designed cam profile and valve lift curve,which lays a good foundation for analyzing the hydraulic fluctuations and valve dynamic characteristics of FHVVS and the osptimization of the mechanism of the system.(4)Through simulation calculation,the lift,speed,and acceleration of the valve under different crankshaft speeds and different drain phase angles are obtained.Simulation results show that the system's valve lift and valve opening duration are continuously fully variable;high speed The performance at the time is good,and there is no out-of-control situation such as valve fly-out,which meets the design requirements and verifies the function of FHVVS.(5)When the crankshaft speed is 2000 r/min and the drain phase angle is 144°,the pressure fluctuations in the high and low pressure system are simulated,and the valve is lifted in four stages.The effects of different speeds on the system's hydraulic fluctuations are analyzed;the effects of some structural parameters on the system are studied,and reasonable adjustments of valve spring stiffness,pre-tightening force,and oil passage diameter can improve FHVVS reliability.By using the elongated rectangular drain hole of the rotor valve,the time value of the valve can be increased while the lift is almost unchanged,thereby increasing the output power of the gasoline engine under the same drain phase angle.