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1. 研究目的与意义（文献综述）

since the invention of automobile, it has played an important rolein people's life and development. with the arrival of the new era, thedevelopment of the automobile industry is more and more rapid, people have moredemand for travel, at the same time, the two words of environmental protectionand sustainable development are becoming more and more important. pure electricvehicle is a new type of vehicle produced under this demand. in order to meetpeople's requirements for the power performance and trafficability of pureelectric vehicles, a reasonable and practical transfer case is needed todistribute the power output from the transmission to each drive axle. thetransfer case is widely used in multi axle drive vehicles. it can reduce the powerconsumption, reduce the wear of tires and transmission parts, transfer thedriving force to the maximum extent, and improve the acceleration andtrafficability of vehicles on various roads. at present, remarkableachievements have been made in the design and production of transfer case inchina, but it still can not fully meet people's demand for vehicle performance.

the transfer case can make full use of theadhesion of four tires and improve the driving direction stability of thevehicle, especially for the pure electric four-wheel drive vehicle. whileobtaining better driving stability, it is conducive to saving battery power andimproving the endurance of the pure electric vehicle. this topic is helpful tothe development of pure electric vehicle industry, to achieve the purpose ofenergy conservation and emission reduction, to promote the rapid development ofsocial economy, and to improve environmental pollution.

in the early stage of the development ofmulti axle drive vehicles, the transfer gears are basically a pair of simplegear transmission systems. but with the development of automobile industry, thedesign of transfer case is more complex and practical. in order to ensure theuse requirements and relatively simple structure, single axle transfer gearsare widely used in vehicles. the single axle transfer case not only simplifiesthe structure of the transfer case, but also makes the operation of the drivereasier. the traditional two axle transfer case requires the driver to manuallyswitch the transfer gear constantly, which is not only cumbersome to operate,but also reduces the driving performance of the vehicle. however, with thedevelopment and wide application of electronic control system, ecu directlycontrols the gear according to the roadconditions and vehicle conditions.

2. 研究的基本内容与方案

1) collect dataaccording to the topic to understand the research topic;

2) selectvehicle parameters, and carry out calculation and design;

3) drawing andmodeling with cad, catia and other software;

3. 研究计划与安排

week1 program idea, literature search andcompletion of opening report.

week2-3 foreign literature translation and data collection;

week4-6 design, calculate and draw the sketch (3.19 opening defense);

4. 参考文献（12篇以上）

[1]wang yuming, research on mechanical characteristics and performance analysis oftransfer case of intelligent four-wheel drive vehicle [d]. anhui agriculturaluniversity, 2012.

[2]liu zhizhu, li zhu, cai weimo, et al. introduction to the development of afull-time four-wheel drive electronic transfer gear assembly [j]. design andresearch, 2019, 131-134

[3]hu fang, tan yudian, wang liang, et al. mechanical characteristics analysis andtest of transfer case bearing of four-wheel drive vehicle [j]. journal of hefeiuniversity of technology (natural science edition), 20171464-1468