Speed Regulation Of Hydro-mechanical Continuously Variable Transmission Considering Working Efficiency

Hydro-mechanical continuously variable transmission(HMCVT)not only can realize continuous and variable change of transmission ratio,so that the vehicle has been running in the best working mode,but also can buffer and reduce the impact of the outside on the system to increase the service life of the transmission system.Therefore,HMCVT is very suitable for engineering vehicles in an operating environment where road roughness and demand power change drastically,and is the focus of research and development in the power transmission industry.Ensuring the efficiency of engineering working is the primary goal of engineering vehicles,and it is necessary to improve the economics of vehicles.The transmission efficiency of HMCVT is a key factor,which directly affects the total power loss and total fuel consumption of vehicles,which affects the vehicles economy.In this paper,the regulation of the speed ratio adjustment of the HMCVT of the loader considering the working efficiency and transmission efficiency is carried out.(1)The characteristics analysis of the loader power transmission system was carried out.The dynamic speed regulation characteristic model and fuel consumption model of a diesel engine were established,and the best power and best economic curves of the engine were obtained.The study of the flow direction characteristics deduces the speed ratio characteristics,torque characteristics and transmission efficiency characteristics of HMCVT.The results show that the transmission efficiency of HMCVT is an important factor affecting the total power loss of the power transmission system.(2)The regulation law of staged speed ratio considering operation efficiency is proposed.Based on the characteristic that the transmission efficiency of HMCVT changes drastically due to the change of operating point,the regulation law of staged speed ratio considering operation efficiency is proposed.In Eco mode,economic speed ratio adjustment strategy is adopted in general transportation conditions,and sport speed ratio adjustment strategy is adopted in joint operation conditions.In Spo mode,sport speed ratio regulation strategy.is adopted in both general transportation conditions and jointoperation conditions.The economic speed ratio adjustment strategy aims at the lowest total power loss of the power transmission system,and the power speed ratio adjustment strategy aims at the maximum output power of the power transmission system and higher transmission efficiency.(3)A simulation study of the loader equipped with HMCVT was carried out.Based on MATLAB/Simulink,the loader model,HMCVT model,driver model and HMCVT controller model were built,and the V-type work cycle simulation analysis was carried out.The results show that,compared with the general speed regulation strategy,the proposed speed regulation strategy in Eco mode reduces the total fuel consumption by 10.50% and the average transmission efficiency increases by 2.68%;in the Spo mode,the total fuel consumption decreases by 6.00% and the average transmission efficiency increases 0.35%.The speed regulation strategy proposed in this paper can reduce the overall fuel consumption while ensuring the efficiency of the loader.