Study On The Power Loss And Cooling System Of CVT Hydraulic Torque Converter

With the development of automobile industry, the serious situation of energy crisis and the advocate of energy-saving and emission reduction, automotive engineering is improving in the requirement of energy saving. Hydraulic torque converter is a key component of vehicle power, which can guarantee the vehicle starting performance and reduce the impact and vibration, is widely applied in the vehicle field. But in actual working process, the hydraulic torque converter has major power loss and produces major quantity of heat which affects the vehicle power and economy performance. Therefore, studying on power loss and cooling system of hydraulic torque converter is helpful to improve the transmission efficiency and vehicle performance.Hydraulic torque converter of continuously variable transmission(CVT) is studied in this paper, the following work have carried out:(1) Based on the flow pattern of torque converter internal working oil, the controlling equation of computational fluid dynamics(CFD) is elaborated, the methods of discretization of the controlling equation are studied, the methods and steps of grid generation and the algorithm of CFD numerical simulation are introduced; The numerical simulation of flow field characteristics of the hydraulic torque converter three working wheels in different working conditions are completed based on FLUENT. The simulation results show that the oil flow inside exists flow separation, countercurrent, and secondary flow which have great influence on the hydraulic torque converter efficiency and power loss.(2) The several forms of power loss in hydraulic torque converter are studied, and the basic theory and equation of heat transmission science are introduced, the heat production formulas and heat conservation equations of hydraulic torque converter are confirmed. The engine with torque converter input characteristics are analyzed and studied, the calculation model of heat production of hydraulic torque converter is established based on MATLAB and the heat production in different conditions are calculated.(3) According to the operating characteristics and actual working conditions of CVT electro-hydraulic control system, an electro-hydraulic control cooling scheme is formulated. Based on the heat production of hydraulic torque converter, the target cooling flow of all components in cooling system are calculated, the main characteristics of hydraulic pump, cooling pressure control valve and throttle valve are studied. Based on the cooling system, the simulation model is established and completed based on AMESim. The simulation results show that, the cooling flow in simulation exceeds the flow in calculation. Then, the verification of simulation is completed by bench test. The test results show that, the simulation model of cooling system is correct and feasible and can satisfy the cooling requirements in hydraulic torque converter.