Power Flow Analysis Of Hydro-mechanical Continuously Variable Transmission

The hydro-mechanical continuously variable transmission(HMCVT for short)includes a mechanical transmission system and a hydraulic transmission system,its purpose is to make full use of the advantages of mechanical transmission and hydraulic transmission,it is widely used in the fields of industrial and agriculture.The internal structure of the HMCVT is complex and the change of system parameters and variables will influence the power flow distribution in the hydraulic circuit and mechanical loop of the transmission,thus changing the transmission performance of the transmission,in-depth analysis and research of the transmission power flow characteristics has an important value in theory and engineering application.The domestic and foreign research on the hydro-mechanical compound transmission is summed up,according to the structural characteristics of hydro-mechanical compound transmission,a total of 12 kinds of transmission schemes of input and output coupling are derived and the theoretical formula of the hydraulic power shunt characteristic of the input and output coupling drives are given.Under the condition of limited part of the parameter values range,comparing the hydraulic power shunt characteristics of each transmission scheme and studying the influence of the displacement ratio e and the planetary row characteristic parameter k on the hydraulic power shunt characteristics of the transmission system.The power flow direction judgment method of input and output coupling transmission is given,and the conditions of various power flow states of the transmission system are summarized,in addition,the efficiency characteristics of the input and output coupling drives are analyzed.The research result shows that the input coupling type is prone to the power cycle of the hydraulic circuit and the output coupling type is prone to the power cycle of mechanical loop.According to the structural characteristics of the CHMCVT,36 kinds of transmission forms of this type transmission are summarized.Within the scope of the limit parameter selection,the structural parameters of 36 kinds of transmission forms are optimized based on the principle of minimizing the average power flow of the hydraulic circuit,and under the optimization parameters,the hydraulic power shunt characteristics of 36 kinds of transmission forms are analyzed and compared,and 7 transmission forms with better hydraulic power shunt characteristics are selected.The power flow direction judgment method of CHMCVT is given,and the 21 kinds of power flow states and their occurrence conditions of the transmission system are summarized.The theoretical derivation and analysis of the efficiency characteristics of the transmission are carried out.The research result shows that compared to the input and output coupling transmission system,the CHMCVT is not easy to generate power cycle which means that the CHMCVT has better power flow characteristics.The experimental analysis of the prototype of the output coupling hydromechanical continuously variable transmission is carried out,the experimental results verify that the output coupling type is easy to produce the mechanical loop power cycle.