| Hydro-mechanical variable transmission(HMT) is a multi-power transmission withthat high power vehicle can realize variable speed and high efficiency. There is an impactin power shift of the HMT. Research results have showed that controlling the pressurevariation reasonably could effectively improve the quality during the power shift.Based on the digital proportional relief valve research, this paper designed ahydraulic control system of a two-range HMT and established its simulation model. Themain contents are as following:(1)The simulation model of digital proportional reliefvalve was established, and experimental study of its characteristics was carried out.Through the simulation comparing with experimental study, results showed that thesimulation model was proved to be correct.(2)According to technology requirements ofthe HMT, a system solution was designed and the parts’ parameters of hydraulic controlsystem were designed.(3)The simulation model of the hydraulic control system wasestablished based on the model of.digital proportional relief valve. The characteristics ofthe hydraulic control system and the conditions that the system worked with the clutchwere obtained through the simulation study. The result showed that the pressure buffercould be realized when the duty ratio of the PWM signal changed in a certain range andthe rule of the pressure buffer changing with the PWM signal was obtained. Besides, acontrol strategy for the process of pressure rising and reducing was formulated. |
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