| Full hybrid system can realize the electric driving mode and recover most of the brakeenergy, which can greatly improve the vehicle fuel economy performance. Hybrid power-trainis an independent electromechanical coupling system, which has been widely regarded as themost practical configuration for present technology. The key development technology ofhydraulic system of a power split hybrid transmission is studied in this thesis.Design theory and method of power split hybrid hydraulic system is studied, and thehydraulic diagram for a hybrid transmission is designed. A new oil supply system of two oilpumps is designed to satisfy the oil flow requirement in EV and hybrid driving modes. Aproportional pressure solenoid valve is used to control the brake engagement pressure, whichcan supply the right needed pressure. The pressure control circulate can decrease the powerconsumption of hydraulic system. Dimensions of the hydraulic valves are designed bytheoretical calculation. Oil flow distribution model is established to distribute the oil flow andobserve the flow and pressure characteristic under different oil temperature and differentdriving modes.Dynamic simulation model of the whole hydraulic system is built to investigate thefunction of hydraulic principle, valve dimensions and characteristics of oil flow and pressurewith ITI-SimulationX. Simulation results indicate the hydraulic system is practical and theelement design parameters can reach the design requirement.Bench test is made to check the function and performance of hydraulic system. The brakecontrol circulation is tested in the case of different given oil flow rate. Test results indicate thebrake engagement pressure control principle is practical, which reach the requirement of theprototype production. The min oil flow rate for the building pressure is confirmed, which canused to guide the pump speed control. |
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