| The hydro-mechanical transmission system is a hybrid transmission system that combines mechanical transmission and hydraulic transmission.The HMT system has the advantages of stepless speed regulation,wide speed range and large specific power,as well as high efficiency of mechanical transmission.The HMT system is divided into an external split type and an internal split type according to the splitting mode,wherein the outer split type uses a planetary gear as a transfer case,and the inner split type uses a hydraulic element as a transfer case.The internal shunt type has good research significance because of its compact structure and ability to avoid power cycle.In this paper,a light crawler tractor equipped with Outer Hydro-mechanical Transmission(OHMT)is used as the research object,an internal hydro-mechanical transmission(IHMT)is designed.The new scheme is to replace the original transmission scheme as a project reservation scheme.(1)Analyzed the OHMT system.Discussed and analyzed the relationship between the hydraulic power ratio and the pump displacement ratio.Using power cycle as the criterion,the torque ratio,the speed ratio and the pump displacement ratio under different operating conditions of OHMT are established.(2)According to the transfer principle of IHMT system,designed an IHMT system based on double cam rotor vane pump.Analyzed the structure and function of unit components in IHMT system and the system transfer process.Calculated and analyzed the speed and torque of IHMT drive,power transfer relationship and hydraulic power ratio relationship;(3)Analyzed the factors affecting the transmission efficiency of the hydraulic mechanical double-flow transmission system.Based on the transmission efficiency of the hydrostatic drive device and the planetary gears,the transmission efficiency models of the internal and external split-type dual-flow transmission system are established.(4)Compared and analyzed the advantages and disadvantages of the internal and external split flow dual-flow drive system,and analyzed the feasibility of the IHMT system,completed parameter matching and calculation for the IHMT system for the target tractor model;(5)Based on Matlab/Simulink,built a whole vehicle model of IHMT system,modeled and simulated the first acceleration and acceleration conditions of the whole vehicle according to the optimal power and best economic strategy.The feasibility of the IHMT system on the tractor is further verified by simulation analysis. |
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