| HMCVT (hydrostatic mechanical continuously variable transmission) is belonging to the field of multi-power flow variable transmission. It can achieve the best match of the engine - gearbox - road load; realize the best fuel economy and dynamic property of the power train system of vehicles. Theory analysis and simulation research of hydro-mechanical variable transmission had been researched in the thesis.The thesis presented an optimum plan of HMVCT. In the MSC Easy5 environment, the simulation model of hydraulic flow transmission mechanism of HMCVT was established, in which the nonlinear component of displacement control mechanism was described by multi-modal based on the states, the analysis shows that the model can adapt to different model of hydraulic flow transmission mechanism of HMCVT. Current response characteristics of electric displacement control mechanism of hydraulic flow transmission mechanism was analyzed, obtained orifice diameter is a great influence factory on their response characteristics, the smaller diameter orifice is, the greater obviously dead zone and hysteretic it will generate, Adopt the method of step control current and appropriate increase orifice diameter can effectively reduce the dead zone and hysteretic. In the shifting of HMCVT, the influence factors of velocity fluctuation and piping vibration of hydraulic component were analyzed, the simulation shows that effectively reduce the velocity fluctuation and the pressure impulse through reduces the pipe length,pipe diameter,hydraulic oil working volume of hydraulic flow transmission mechanism and extend the time of reverse torque. The relation between speed and volumetric efficiency of hydraulic power transmission system was analyzed, the results indicated that the velocity fluctuation is decrease when volumetric efficiency is increase. In order to offset the impact of volumetric efficiency,reduce the displacement of variable displacement hydraulic component when the torque is reversed, which can effectively reduce the velocity fluctuation of fixed displacement hydraulic component.This research shows that the measures, which reduce velocity fluctuation and piping vibration of hydraulic component in the process of shifting changes, can effectively improve shift quality and dynamic characteristics of HMCVT. |
