Design of multi-range hydro-mechanical transmission using modular method

•Multi-range hydro-mechanical transmission is designed by using modular method.•Two-phase PS mechanism acts as the basis of gear ratio extension.•Normalised efficiency map of PS mechanism is derived with motor variables.•A multi-range HMT matched to a heavy duty vehicle has been simulated and tested. This paper introduces a kind of multi-range Hydro-mechanical transmission (HMT) based on dual stage input coupled layout. To extend the gear ratio, a new design method is presented in this research. A two phase (positive and negative) power split mechanism is designed based on the hydrostatic circuit. It can realize the continuous speed regulation in a complete motor speed cycle. Continuous speed regulation is carried out to be independent with the characteristic parameters of planetary in this mechanism. On the basis of it, the speed range of HMT can be extended very well. Further, the speed, power flow and normalized efficiency of the PS mechanism is analyzed in detail. Two kinds of power flows are validated to live in every hydro-mechanical range. A multi-range HMT is proposed and matched with a heavy duty vehicle. To obtain the performance of the HMT, a simulation model will be built in the AMESim and a corresponding test bench will be run to verify the characteristics. The proposed HMT presents a mean efficiency about 83% in a wide speed range.