Research On Valve Switching Mechanism Of Hydraulic Variable Stroke Engine

Variable-stroke engine can improve engine power without changing the engine displacement and quality, especially the power at low speed and high load condition. The key for variable-stroke engine is to realize the switching of valve mode with ignition, injection and turbocharger, so as to realize the switching between the two-stroke mode and four-stroke mode. Based on the valve mechanism of Honda WH-125 engine, a hydraulic valve switching mechanism with two kinds of air distribution mode is designed.The valve switching mechanism designed in this paper can realize the switching of the two valve mode, in which the switching action is realized by oil pressure. The Cam mechanism is mainly consisted of three sections: a sprocket shaft, a cam body and a right shaft. The cam combines the intake and the exhaust cam of both two-stroke mode and four-stroke mode. In two-stroke mode, the cam in air valve mechanism is designed as bimodal cam to avoid the gear ratio contradiction between the crankshaft and camshaft. The switching range of valve mechanism is determined by the gas phase and the cam arrangement.In this paper, the CAM structure is equivalent to a hydraulic cylinder model, appropriate components are selected according to theory and computation, a hydraulic simulation software AMESim is used to simulate the hydraulic system. The pressure of hydraulic cylinder, the stress of piston and the piston motion during valve mode switching are analyzed to determine the working pressure of hydraulic system; The switching time is determined by both cam structure and hydraulic simulation results.The physical model of the valve mechanism is established by 3D modeling software, dynamic characteristics of valve mechanism in a single-stroke engine mode is analyzed using a dynamic simulation software ADAMS.; Cam motion decided by the force applied on both ends of the cam body, which can realize the switching of two valve modes. The valve characteristics and contact force during mode switching are analyzed, and then the rationality of the valve design is obtained by dynamic simulation.Machine the designed valve mechanism, design a test to get valve performance of valve mechanism, then test and verify valve mechanism according to the working requirements. Test the CAM switch time under different pressure to determine the working pressure of hydraulic system. At the same time, the test can verify the reliability of the hydraulic system.