Theory Analysis And Simulation Of The Composite CVT System

CVT (Metal V-belt Continuously Variable Transmission) is one of perfect transmission of cars, which has been greatly applied in transmission of cars and can improve power and fuel economy. However, it can't be used in transmission of larger power vehicles because of the limited speed ratio coverage and maximum output torque. The Composite CVT System can improve the speed ratio coverage and the maximal output torque of CVT, and enlarge application range of CVT. Theory analysis and simulation of the composite CVT system had been researched in the thesis.The thesis presented a optimum plan of composite CVT system, deduced the formula of output speed of the composite CVT system in the positive and negative phases as well as the relationship between each range when exchanged the ranges, obtained mathematical formula between the dual-mode power summing planetary gear sets parameters and derived the value range of k z, k fand? . The power flow forms of composite CVT system in positive and negative phases were analyzed, formulas of its torque and diffluent power ratio were deduced, it's concluded that the diffluent power ratio was determined by the planetary gear set, has nothing to do with the ranges and its size depended on the geometric ratio value? and the CVT speed ratio coverage. Formulas of overall transmission efficiency of the composite CVT system in positive and negative phase were deduced, the model of overall transmission efficiency was established by MATLAB simulation software, the efficiency curve was obtained by simulation, and the relation between overall transmission efficiency and CVT efficiency CVT transmission ratio, transmission torque or input speed was analyzed. The results indicated that the overall transmission efficiency was improved as CVT transmission ratio, transmission torque and input speed increased.The research indicates that the composite CVT system not only expands the speed ratio coverage of CVT as well as improves transmission power and output torque, but also has significantly higher efficiency than CVT transmission. Therefore, the composite CVT system is suitable for larger power vehicles.