1. 研究目的与意义（文献综述）

as an important part of the automotive transmission system, the transmission has a direct impact on the power and economy of the vehicle, the reliability and portability of the operation, and the smoothness and efficiency of the transmission. although the conventional manual transmission has many shortcomings such as large shift shock, large volume, and inconvenient operation, it is still widely used in modern automobiles because of its high transmission efficiency, mature manufacturing technology and low cost. today, although automatic transmissions are becoming more and more popular, manual transmissions still occupy a large market share. it directly affects the dynamics, fuel economy, transmission stability, and handling stability of automobiles. compared to automatic transmissions, manual transmissions are slightly more complicated in operation, but they can give car drivers a better operating experience, higher transmission efficiency, and better fuel economy. manual transmissions are also more powerful than automatic transmissions, allowing the car to accelerate or overtake in a shorter time. in addition, after many years of research on manual transmissions, all aspects of technology have been very mature, and manufacturing and maintenance costs are lower.

research state in china(国内研究现状):

at present, the changes in the new powertrain assembly for passenger cars in china are mainly reflected in two points: first, the engine power level is increasing; second, the use of passenger-specific transmissions is increasing; the transmission of high-torque passenger cars is increasing; and the full synchronizer technology is widely used. synchronizers are also being researched and developed. the use of shifting pneumatic booster technology has begun, and the matching of eddy current retarders has also increased. the automatic transmission has become a new project for research and development by major companies.the domestic passenger car transmission is further developing and perfecting the serialized spectrum, and gradually forming a 5-speed bus transmission series and 6-speed coach and intercity bus series as well as light bus series. the center distance is obviously serialized and achieves the generalization of most parts and tools. expanding the product range of passenger car transmissions is the development goal of all kinds of passenger car transmission factories in china. it is necessary to improve the series of passenger car transmissions. the manual transmission should be the first product to be considered. from the perspective of the development of foreign product technology and the development of passenger train transmissions, the manual transmission is still the mainstream configuration of passenger cars for a long time. from a long-term perspective, the serialization of amt transmissions is a strategic issue that needs careful study.

2. 研究的基本内容与方案

The main function of the automobile transmission is to increase the range of torque and speed change that the engine transmits to the driving wheel of the vehicle to meet the requirements of different conditions of use. At the same time, under the conditions of keeping the engine running smoothly, it can meet the requirements of the car reversing. In the actual use of city buses, there is basically no need for first gear, starting with the second gear, and directly changing the third gear after the start; because the city bus is running on a good road, the speed and acceleration are more demanding. Its first gear ratio is generally small. From the perspective of ride comfort, the gear compartment spacing (ratio of gear ratio) of the passenger car is preferably 1.3 to 1.4. Transmission ratio ratio distribution, the interval between the first and second gear is the largest, and the second and third gears are followed by the interval. The other gears gradually decrease according to this law.

The gear is basically set to five forward gears (including the highest gear) and one reverse gear. The basic structure of the five-speed passenger car transmission is still the assembly of the three major assemblies (one-axis, two-axis, and intermediate shaft). After the preliminary design is completed, CATIA is used to perform three-dimensional solid modeling of gears, shafts, and housing components to check the assembly interference.

3. 研究计划与安排

1~2 (19th and 20th weeks of the 7th semester): determine graduation design topics, graduation design assignments (related parameters), and collection of information on campus

3 (1st week of 8 semesters): plan conception, literature search, completion report

(2-3 weeks of 8th semester): off-campus internship, off-campus data collection, completion of internship report

4. 参考文献（12篇以上）

[1]綦力. 手动变速器的技术特点及发展趋势[j]. 商用汽车,2009,02：110-112，115.

[2]李晓宁. 客车变速箱研究与设计[d]. 吉林：吉林大学,2015.

[3]刘诏书，肖佩，李刚炎. 研发客车变速器的必要性及方向[j]. 汽车研究与开发，2003,02：12-14.