毕 业 论 文

（科 学 研 究 报 告）

题 目

院(系)别 专 业 级 别 学 号 姓 名 指导老师

汽车发动机四缸曲轴加工工艺

及夹具设计

机电及自动化学院 机械工程及自动化

2009 ***** *** *** 副教授

** 大 学 教 务 处 2013年6月

1

摘 要

曲轴是汽车发动机的重要零件。它的作用是把活塞的往复直线运动变成传动轴的旋转运动，将作用在活塞的气体压力变成扭矩，用来驱动工作机械和发动机各辅助系统进行工作。曲轴在工作时承受着不断变化的压力、惯性力和它们的力矩作用，因此要求曲轴具有强度高、刚度大、耐磨性好，轴颈表面加工的尺寸精确，且润滑可靠。

本设计是根据被加工曲轴的技术要求，进行机械工艺规程的设计，然后运用夹具设计基本原理和方法，拟定夹具设计方案，完成夹具结构设计。主要工作有：绘制产品零件图，了解零件结构特点和技术要求；根据生产类型和所在企业生产条件，对零件进行结构分析及工艺分析；确定毛坯种类及制造方法；拟定零件机械加工工艺过程，选择各工序的加工设备与工艺设备，确定各工序的加工余量与工序尺寸，计算各工序的切削用量与工时定额；填写机械加工工艺过程卡片、机械加工工序卡片等工艺卡片；设计指定的专用夹具，绘制装配总图和主要零件图。

本次设计主要是为了提高曲轴零件的生产效率，以及加工精度。因此，制定工艺路线时严格按照基准先行，先主后次，先粗后精，先面后孔的工艺设计准则。先加工出基准，再用

精基准定位加工其它工序。在夹具设计时，选择的是车曲轴连杆轴颈的工序，定位时选择两个V形块和周向定位钉定位，用压板夹紧，并且在夹具上设置合适的偏心距。

通过本次设计我查阅了许多书籍和行业资料，了解到行业的发展进程和部分先进技术，扩展了我的专业视野，为将来的学习生活都有着重要的影响。

关键词：机械制造，加工工艺，曲轴，夹具

I

ABSTRACT

Crankshaft is a very important parts of diesel engine. Ist action is change the to and fro

straight-line motion of the piston into rotary motion,and change the gas pressure on the piston into torque, that is used to drive executive body and accessory system of the diesel engine. Crankshaft is withstanding the changing pressure, inertia force and the torque. So the crankshaft mast have high strength, high rigidity, high abrasion resistance and the surface of axle journal must have high precision with well lubricating.

This design is on the basis of technical requirement of the crankshaft to design the technological procedure. And then use the fundamental and method of the fixture design to fix the fixture design programme,and complete the structural of the fixture. The main work is: Parts drawing, understand the characteristic of structure and technical requirement; Accroding to the types of manufacturing and the plant conditions of the company we will analyse the structure and craft of the crankshaft; Fix the type and manufacturing method of the roughcast; Fix the processing technic of the crankshft,select device and equipment fix the machining allowance and working procedure size and count the cutting specifications and time allowance.; Fix the Processing technological process card and Machine-finishing operation card; Design the special fixture and plan the assembling drawing and main parts drawing.

This design is in order to improve the crankshaft parts production efficiency, and the machining accuracy. Therefore,when drawing up the process we strict accordance with the design criteria that

benchmark first,main first then secondary, rough first then essence, surface first ，hole after . First, work out benchmark, again with pure reference positioning processing other processes. In fixture design,I choose the car process of crankshaft connecting rod , When location,I choose two V block and

circumferential locating pin to positioning, pressed powder compact, and set up appropriate eccentricity on the jig.

Accroding to this design I looked through many books and industry information, understand some of the industry development process and advanced technologies,and also expanded my professional field.It has important influence on my future study and life.

KEYWORDS: Machine manufacture Processing craft Crankshaft fixture

II

目 录

摘 要 .................................................... I ABSTRACT ................................................. II 第一章 绪 论 .............................................. 3

1.1设计的主要内容 .................................................... 3 1.2国内外的研究现状 .................................................. 3

第二章 零件分析 ............................................ 7

2.1零件的作用 ........................................................ 7 2.2曲轴工艺分析 ...................................................... 7

第三章 工艺规程设计 ........................................ 8

3.1确定毛坯的材料和制造形式 .......................................... 8 3.2基面的选择 ........................................................ 8

3.2.1粗基准的选择 ....................................................................................................... 8 3.2.2精基准的选择 ....................................................................................................... 8

3.3制定工艺路线 ...................................................... 8 3.4工艺路线方案 ...................................................... 9 3.4机械加工余量、工序尺寸及毛坯尺寸的确定 ........................... 10

3.4.1确定加工余量 ......................................................................................................10 3.4.2确定工序尺寸及其公差 ........................................................................................ 11 3.4.3加工余量计算 ...................................................................................................... 11

3.5确定主要工序的切削用量及基本工时 ................................. 16

第四章 专用夹具设计 ....................................... 37

4.1设计主旨 ......................................................... 37 4.2需要解决的主要问题 ............................................... 37

4.2.1形状复杂 .............................................................................................................37 4.2.2刚性差 .................................................................................................................37 4.2.3技术要求高 ..........................................................................................................37

4.2确定夹具设计方案 ................................................. 38

4.2.1选择定位基准，并确定工件的定位方式及定位元件的结构 ....................................38 4.2.2确定工件的夹紧方式，选择合适的夹紧机构 .........................................................38 4.2.4确定铣床夹具与机床间的正确位置 .......................................................................39

4.3夹紧力的计算 ..................................................... 39

4.3.1切削力的计算 ......................................................................................................39 4.3.2工件正确夹紧所需力的计算 .................................................................................40 4.3.3螺钉夹紧力 ..........................................................................................................40

4.4夹具的定位精度分析 ............................................... 40

1