Efficiency analysis of an innovative multi-range hydro-mechanical continuously variable transmission

To study the calculating method of the total efficiency of the innovative multi-range hydro-mechanical continuously variable transmission (HMCVT) when factors such as the power cycle and the variation of the efficiency of hydraulic units with their input power are considered, this paper established an approximate efficiency formula of hydraulic units according to test data, given an efficiency algorithm of the closed pump-motor system, which varies with the speed, pressure and displacement of hydraulic units, derived the existence conditions of the power cycle in the closed planetary gear transmission, presented the efficiency formulas of typical structures of HMCVT, and described a reasonable efficiency calculating procedure. The efficiency of the innovative multi-range HMCVT is calculated by this procedure. The result shows that the average efficiency of HMCVT is higher than 0.93, although the efficiency varies with the transmission ratio, the input power and speed. The HMCVT can work in high efficiency ranges by properly adjusting its transmission ratio into the ranges that the pump displacement is near to zero.