中型货车变速器设计（三轴式）
摘   要
三轴式变速器由于具有体积小、原理简单、工作可靠、操纵方便等优点，故在大多数汽车中广泛应用。本次设计的目的主要是基于对机械原理、机械设计、AutoCAD等知识的熟练运用和掌握，同时运用汽车构造、汽车设计、材料力学、互换性测量等学科知识，对三轴式变速器的各部件进行设计。
首先，本文将概述汽车变速器的现状和发展趋势，介绍变速器领域的最新发展状况。
其次，本文将对不同的变速器传动方案进行比较，选择合理的结构方案进行设计。
再次，本文重点对变速器的两种重要部件—轴和齿轮进行受力分析,强度、刚度的校核计算，以及为这些元件选择合适的工程材料及热处理方法。
最后，本文将对变速器换档过程中的重要部件—同步器以及操纵机构进行阐述，讲述同步器的类型、工作原理、设计方法以及重要参数。
在附录中，本文还将给出进行计算的必要公式、表格及图形，供参考之用。
 
关键词：变速器，同步器，轴，齿轮
Design Three-shaft Transmission for Medium-duty Truck

Abstract
Three-shaft transmission is widely used most vehicle for its particular advantages ,such as small dimension ,simply theory ,good stability, conveniently operation .The purpose of my paper is based on the skillful of using mechanic theory ,mechanic design, AutoCAD. Meanwhile, my paper is incorporated structure of vehicle, design of vehicle, mechanic of materials, and survey of interchangeability. I will design the parts of three-shaft transmission.
At first, I will give a summary of the current situation and the tendency of development of the vehicle transmission, and introduce the latest development state in the field of the transmission.
The second, I will compare the transmitting scheme of different transmission, and choose a better structure scheme.
Next, I will do some mechanic analyses, strength, stiffness check of the shafts and gears, which are the important parts of the transmission, and choose appropriate materials and heat treatment.
At last, I will introduce the operation mechanism and the synchronizer, which plays an important role in changing gear. I will give an account of the type, operation, design procedure and major parameter of the synchronizer.
At the supplement, I will write some thing like formula, tableau graph and so on. It may be helpful for the future design.
 
Key words: Transmission, Synchronizer, Shaft, Gear