Study On Valve Movement Characteristic Of Si Engine With Fully Variable Hydraulic Valve System

The continuous variability of maximum valve lift, opening duration and valve timing can be attained by using fully variable valve system (FVVS) in gasoline engine, which is beneficial for improving engine performance. The system presented in this paper is one kind of hydraulic variable valve system, named SDFVVS, which is applied to EQ486 gasoline engine The intake valve is opened while the hydraulic piston is driven by the cam shaft. A rotatory mechanical valve is used to control the oil pressure, once the pressured oil is collapsed, the intake valve starts to seat, then a seating snubber unit is actived to control the valve seating speed. The SDFVVS has the advantages of higher limited response frequency (mechanical structure), better reliability and lower cost, as the solenoid valve was replaced which applied in traditional hydraulic variable valve mechanism.The experiments were conducted to investigate the performance of SDFVVS, the main work can be concluded as three aspects as follows:(1) The establishment of experiment setup. To meter the intake valve lift curves, a EQ486 was modified, The origin intake cam shaft drive system was improved. A electric motor was selected to drive the cam shaft, the real working condition of the engine was simulated. A Laser displacement sensor was selected and installed to measure the intake valve lift with high accuracy. The hydraulic system in engine was refitted to supply oil to the SDFVVS and lubricate the engine well.(2) The measurement of intake valve lift. The intake valve lift was measured and experiments results show that, the maximum valve lift and opening duration are increased with engine speed and the oil collapsing angle. Engine speed has limited effects on the intake valve lift and the oil collapsing angle determines the final valve lift profile. With regard to the seating speed, engine speed has little effects on the seating speed, and the maximum valve lift affects the seating speed. The results show that, the seating speed is increased with the maximum valve lift. The experiment results further show that,the continuous variability of maximum valve lift, opening duration and valve timing can be attained by using SDFVVS.The feature that different cylinder has the uniform intake valve lift can satisfy the requirement of multi-cylinder engine.(3) Investigation of interference between neighbouring intake valves. SDFVVS has the characteristic that the first and the second cylinder shares one accumulator, the third cylinder and the forth cylinder shares one accumulator. The interference between neighbouring intake valves caused by the characteristic. The manifestation of the interference between neighbouring intake valves was the valve opened earlier will bounce secondly. The phenomenon which can be clearly observed under medium oil collapsing angle and high engine speed. The cause of this phenomenon was studied in detail and a solution is proposed to avoid this bounce.