Design And Study On The New Typed Hybrid Power Transmission System Based On CVT

Facing with the situation that global oil resources are depleting and environmentalpollution increasingly serious problems, human beings must find a way bothenergy-saving and environmental protection, and yet continue to enjoy the benefits ofconvenience life and rapid social development brought by vehicles. Since nobreakthrough in key technology of fuel cell vehicle and pure electric vehicle, to develophybrid electric vehicle has become the most effective solution to solve the problem.Hybrid power transmission system is a core part of the hybrid electric vehicle.According to the vehicle-type to be developed, to select and design a hybrid powertransmission system that structure is compact, operating mode is complete relativelyand easy to control is the key to develop hybrid electric vehicle successfully. In thepaper, after analyzed and contrasted the pros and cons of domestic and abroad powercoupling systems and transmission systems used in hybrid electric vehicle, four newcompact hybrid power transmission systems that combined the power coupling functionof planetary mechanism and the continuous ratio changing characteristics of the CVTare proposed and designed. And a wide range of research work on the hybrid powertransmission systems designed is carried out. The main contents of the paper are asfollows:①The structure and characteristics of power coupling systems and transmissionsystems of hybrid electric vehicles existed are analyzed. Several typical transmissionsystems of hybrid electric vehicle are described, and the trend of development of hybridpower transmission is pointed out. According to the function requirements of the hybridpower transmission system, and through using the method of lever analogy to analysisfeatures of single and dual planetary mechanisms, four new typed hybrid powertransmission systems based on CVT are designed. Varieties of operation modes underdifferent vehicle driving conditions, and coupling characteristics of different operationmodes are analyzed.②Taking one prototype car as reference object, parameters of the power sourcesystems and transmission systems involved for the design scheme of one new typedhybrid power transmission are matching designed and studied. Combine thecharacteristics of the power transmission operation modes, the parameters matchingdesign of parts including the engine, motor/generator, battery pack, the planetary mechanism, continuously variable transmission final drive etc are completed.③According to structure of the new typed hybrid power transmission system andits operation modes characteristics, and aim to meet automobile power performance andto improve fuel efficiency, the whole vehicle control strategy is established, includingthe engine operating region control, motor control, CVT speed ratio control,regenerative braking force distribution control, operation mode switching control etc.④On the basis of Matlab/Simulink simulation model of the vehicle powertransmission system based on the whole vehicle control strategy is established. Powerperformance simulation of the new typed hybrid power transmission system at the pureelectric operation mode, the engine alone drive mode and the hybrid drive mode arecarried out. And simulation of the fuel economy in the NEDC, UDDS, and1015drivingcycle are also carried out. The results show that the power performance and fueleconomy in driving cycles of the new typed hybrid power transmission system based onCVT designed has obvious advantages, and it can well positioned to meet theperformance requirements for hybrid electric vehicle.