1. 研究目的与意义（文献综述）

the transfer case is an important part of the automatic transmission which is widely used in multi-axis drive systems because of the multi-axis drive vehicle having high requirements for power, off-road passing, response speed, and reliability [1]. the power output of the transmission is distributed to each drive axle by the transfer case with the driving torque being transmitted to the highest extent, which improves the dynamic, acceleration and passability of the vehicle under various road conditions [2].

the mechanization and electronic development of the transfer case in the western countries such as the united states and europe came earlier. after two gulf wars, the exhibition has become more perfect. the structural features of the foreign transfer case are that the front output shaft drive system adopts low-noise multi-row chain drive. domestic transfer cases are mainly based on counterfeiting of foreign products. it have certain innovation ability with there being still a certain gap compared with foreign advanced technology [3-5].

there are many forms and types of transfer cases whose core performance is the difference of technical route choices. according to different judgments, the standard can divide the technical route used in the transfer case into different categories. most transfer cases are slowing down the role of torque increases with higher load than the transmission, thus the transfer gear constant gears are helical gears, bearings are used apered roller bearings. according to the different number of shifts, transfer cases can be divided into single-speed transfer cases and double-speed transfer cases;according to the power size, it can be divided into small power transfer case and high power transfer case; according to the number of output shafts, it can be divided into two-axis, three-axis, etc.; according to the different torque distribution it can be divided into symmetrical, asymmetric, twist ;whether the moment changed it can be divided into fixed torque type, variable torque type [6, 7];

2. 研究的基本内容与方案

the main content of this design:
1. master the working principle of the off-road vehicle transfer case;
2. establish a three-dimensional geometric model of the off-road vehicle transfer case;
3. intensity analysis of key components of the off-road vehicle transfer case: including verification of the shaft, verification of gears, checking of gear contact strength and checking of gear bending strength;
4. perform kinematic analysis of the off-road vehicle transfer case.

to determined the dimension parameters through calculation and verification of each component, and to draw parts and general assembly drawings using cad.

3. 研究计划与安排

Week 1: Collect dissertation-related papers, patents, and other information.
Weeks 2-3: Project Concept, Completion Report, Foreign Language Translation
Weeks 4-5: Off-campus internship, off-campus data collection, completion of internship report
Week 6: Data Processing, Completion of Foreign Language Translation
Weeks 7-9: Design Calculations, Sketching
Week 10-12: Drawing, Writing Design Calculation Instructions, Pre-Defense
Week 13-14: Pattern and design calculation manuals, information kits, and qualifications for review
Week 15: Student's application for reply and prepare for reply; teacher review drawings and instructions
Week 16-17: Attendance

4. 参考文献（12篇以上）

[1]洪福生. 国外越野车发展的新动态[j]. 汽车与配件,1996,24:17-13.

[2] 史建鹏,孙庆合. 分动器转矩分配比确定理论研究[j]. 汽车工程,2007,10:889-892.