Energy Consumption Analysis of 2Z-X(B) Planetary Input-Coupled Hydro-Mechanical Tractor Transmission

The hydro-mechanical transmission (HMT) of continuously variable transmission tractors typically achieves speed regulation using a 2Z-X(A) planetary gear system. Long-term use of this setup has created a strong patent barrier, hindering further HMT structural innovation. This study systematically examines the energy consumption characteristics of HMTs based on a 2Z-X(B) planetary gear set configuration, aiming to provide a theoretical reference for developing new HMT tractors. First, the powertrains of both 4-range and 2-range HMTs using this configuration are described. Next, a mathematical model of the 4-range HMT is developed, and its hydrostatic power portion, transmission efficiency, and fuel consumption are analyzed. Finally, the energy consumption characteristics of the 2-range HMT are compared with those of the 4-range HMT, highlighting their performance differences. Results indicate that HMTs based on the 2Z-X(B) planetary gear set exhibit similar efficiency characteristics to traditional systems, with a maximum efficiency exceeding 90%. The impact of efficiency on HMT fuel economy is greater than that of engine fuel consumption itself, suggesting that an efficiency-prioritized power matching control strategy is feasible.