Development and application of a measurement system for variable hydraulic valve motion in a multicylinder engine
[Objective]The variable displacement technology(intelligent cylinder deactivation technology)can stop part of the cylinder under partial load,reduce pumping and heat losses,and improve the fuel economy and thermal efficiency of the engine.This new technology has gradually become a hot topic in the field of efficient and clean internal combustion engines.The simple and reliable actuator is a key and important prerequisite for the application and testing of variable displacement technology.In this study,the hydraulic variable-valve mechanism of a four-cylinder engine was developed independently,and it lays the foundation for research on variable-displacement valve control strategies.[Methods]The variable valve mechanism designed in this study is mainly composed of low-pressure and high-pressure systems and a seating buffer mechanism.A low-pressure system is used to ensure that the pipeline of the variable valve mechanism is filled with hydraulic oil.The discharge of hydraulic oil in the high-pressure system can be controlled by opening the throttle valve,and the maximum pressure in the mechanism and piston chamber can also be adjusted to achieve continuous variables of valve lift and timing.The valve seating system reduces the flow rate during the valve-closing process and plays a cushioning role.To reduce the development cycle and save costs,the influence of various factors on the test platform under the condition of reducing the number of tests needs to be explored.According to the characteristics and working principle of the variable valve mechanism components,a simulation model of the hydraulic variable valve mechanism of a four-cylinder machine was built using the HCD library of AMESim software.Through the combination of experiments and AMESim simulations,the influence of key parameters,such as valve spring stiffness,valve piston mass,and throttle hole size,on the pressure fluctuation of the system is explored,and effective measures are taken to reduce the pressure fluctuation.These findings lay the foundation for optimizing the key components of variable valve mechanisms.A hydraulic variable valve motion test platform was built,and the flexible variable valve motion characteristics were investigated.The valve lift and closing time,valve opening and closing mode conversion,and valve motion consistency were analyzed by conducting experiments.[Results]Results showed that the valve lift continuously varies between 0 and 9.5 mm,the valve seating speed is less than 0.5 m/s,and the valve closing time can be advanced by approximately 100° CA.During different engine cycles,the maximum and minimum valve lift errors among the four cylinders are less than 0.77%.As the valve opening lift or engine speed increases,the transition period required for the valve opening and closing mode conversion increases,and the maximum transition period is 0.6 s.[Conclusions]The hydraulic variable valve mechanism and the flexible variable valve motion characteristic measurement system of the four-cylinder engine developed are good and reliable.The key problems,such as function design,structure design,measurement,and control software module development,are solved.The research results are conducive to the realization of high-efficiency,energy-saving,and clean new technology for internal combustion engines and lay the foundation for the test platform of the study of the variable displacement valve control strategy.
hydraulic variable valve mechanismvalve motion characteristicsAMESimtest system
万方数据
维普
