The Efficiency of multi-range hydromechanical stepless transmission

To determine the efficiency of multi-range hydro-mechanical stepless transmission (HMT), a general model of HMT was structured, and on the basis of power flow analysis, the efficiency function was obtained. The efficiency of multi-range HMT changes continuously with output speed in each range and is higher than the highest point of the hydraulic efficiency. The volumetric efficiency can potentially result in the speed fluctuation, which can be reduced or eliminated through controlling the ratio of the displacements of hydraulic units properly or changing the point of range exchanging. And the mechanical-hydraulic efficiency of the fixed unit can bring about different pressure under the condition of constant output torque or different output torque under the condition of constant pressure when the transmission works in different part of range. The research shows that multi-range HMT is an ideal stepless transmission with high efficiency.