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1、Chapter 3 Planar Linkages Mechanisms and its Design (平面连杆机构及其设计),Questions： 1、What is Condition for having a crank (Grashof Criterion) in Four-bar Linkages Chain(铰链四杆运动链中，转动副为整转副的充要条件是什么?) 2、What is quick return characteristics of mechanisms(什么是机构的急回特性)？ 3、How to avoid the dead-point position(如何克服死点
2、位置)？,Important contents (重点掌握的内容)： 1、Types of Four-bar Linkages (铰链四杆机构类型判断) 2、The equation of coefficient of travel speed variation and its application(行程速比系数公式及应用) 3、Design of Planar Linkage Mechanisms(平面四杆机构运动设计),Study object: Planar Linkages Mechanism,What is the planar linkages mechanisms (什么是平
3、面连杆机构)？,The mechanisms are composed of lower pairs and links(由连杆和低副联结而成的机构)。 It is lower-pair mechnisms(或称低副机构)。,Crank-rocker mechanism,Ellipsograph mechanism 椭圆规机构,Crank-slider mechanism,Crank Press 冲床,Planer刨床,Gear planer插齿机,All above it application. What is the characteristics of planar linkages
4、mechanism?,3-1Characteristic of linkage mechanisms and its design (连杆机构的特点及其设计的基本问题),Planar linkage mechanisms平面连杆机构。,Planar linkage mechanism is popular in industrial application. 平面连杆机构有诸多优点被广泛应用。,1. Types of linkage mechanisms(连杆机构的分类)：,（1）According to relative motion of links (根据其构件间的相对运动分类)。,Sp
5、atial linkage mechanisms空间连杆机构。,Four-bar linkages 四杆机构。,（2） According to number of links (根据构件的数目分类)。,Five-bar linkages五杆机构。,杆机构。,一、Characteristics of mechanisms,2. Advantages of planar linkage mechanisms (平面连杆机构的主要优点)：,（2） The contact pressure stress is lower,and it is easy to manufacture. (低副不易磨损而
6、又易于加工)。,（1） It can perform many motion (能够实现多种运动轨迹曲线和运动规律)；,（3）Structure is simple(几何封闭，结构简单)。,3-1 Character of linkage mechanisms and its design (连杆机构的特点及其设计的基本问题),3. Disadvantages of planar linkage mechanisms (平面连杆机构的主要缺点)：,（1）Inertia force and inertia moment(惯性力及惯性力矩)。,（2）Approximately achieve an
7、ticipated motion (近似实现预期的运动规律，设计方法复杂)。,（3）Cumulative error(造成累计误差)。,4. Application(平面连杆机构的应用)：,light industrial machinery, agricultural machinery (轻工机械、农业机械等)。,（连杆机构作变速运动的构件引起振动和噪声的主要原因，如纺织厂，噪音污染十分严重，现在有所改善，但机构决定不可避免）,5. Development trend发展趋势：,Computer aided design(计算机辅助设计是一大趋势)。,3-1 Character of li
8、nkage mechanisms and its design (连杆机构的特点及其设计的基本问题),1. Implement anticipated motion (实现预期的运动规律),Molding machine 造型机的翻转机构,3-1 Character of linkage mechanisms and its design (连杆机构的特点及其设计的基本问题),Transverse planing machine牛头刨主体机构,二、Basic Section of Design 设计的基本问题,2. Implement anticipated moving track 实现预期
9、的运动轨迹,Crane起重机,Blender搅拌机,3-1 Character of linkage mechanisms and its design (连杆机构的特点及其设计的基本问题),二、Basic Section of Design 设计的基本问题,Four-bar Linkages is most popular in planar linkage mechanisms. 平面连杆机构中结构最简单、应用最广的，是四杆机构!,3-2 Types of Four-bar Linkages and its evolution 平面 四杆机构的基本形式及其演变,一、Four-bar Lin
10、kages平面四杆机构的基本形式-铰链四杆机构,Slide link 连架杆,Frame机架,Slide link 连架杆,Coupler连杆,能绕其轴线转360的。,仅能绕其轴线作往复摆动的。,Crank曲柄:,Rocker摇杆:,2.Composition 组成,All pairs are revolute pairs in a four-bar mechanisms 所有运动副全为转动副的四杆机构。,1. Definition：,Frame机架：固定架。,做平面运动的构件。,Coupler连杆:,连架杆,According to two slide links, types of Fou
11、r-bar linkages are as following:按照两连架杆的运动形式的不同,可将铰链四杆机构分为：,Crank-rocker mechanism曲柄摇杆机构,Double-crank mechanisms双曲柄机构,Double-rocker mechanisms双摇杆机构,一般曲柄为原动件.P364破碎机、缝纫机,3.Types分类,(1) Application of Crank-rocker Mechanisms 曲柄摇杆应用举例,Blender搅拌机,Device for training legs下肢力量训练器,4. Application应用,Radar scan
12、ning aerial雷达扫描天线,Fly shear飞剪机构,Sewing machine缝纫机,(2) Application of Double-crank Mechanisms双曲柄应用举例,Train wheel 机车车轮,Unbalanced-throwscreen惯性筛,(3) Application of Double-rocker Mechanisms双摇杆应用举例,Aircraft landing gear飞机起落架,A,D,地面,All above are basic definition, composition, types and application of Fo
13、ur-bar Linkages.,二、 Evolution of Four-bar Linkages 平面四杆机构的演化,Replacing a revolute pair with a sliding pair 转动副转化成移动副的演化,crank and translating guide-bar mechanism 曲柄移动导杆机构,in-line(对心) slider-crank mechanism,eccentric (or offset)(偏置) slider-crank mechanism,对心曲柄滑块机构,偏置曲柄滑块机构,曲柄滑块机构（对心）,曲柄当滑块机构（偏心）,Ecce
14、ntric (or offset)(偏置) slider-crank mechanism,In-line(对心) slider-crank mechanism,曲柄滑块机构 Crank-slide mechanisms,2. Enlarging(扩大) a revolute pair 扩大回转副,Evolution 演化：,偏心轮机构 Eccentric mechanism,曲柄滑块机构 Crank-slide mechanisms,2. Enlarging(扩大) a revolute pair 扩大回转副,Evolution 演化：,偏心轮机构 Eccentric mechanism,Ec
15、centric mechanism 偏心轮机构,Application：,Advantages：,High strength, high rigidity, easy to make. 强度高，刚度高，且便于加工制造。,Transfer big force. 用于传递较大力场合。 如破碎机、冲床、剪床、内燃机等。,3. Taking different links as the frame取不同构件为机架,Crank-rocker mechanism,Double-crank Mechanisms,Double rocker Mechanisms,由铰链四杆机构动画知取不同构件为机架各构件间的
16、相对运动关系不变，得到四种机构,曲柄摇杆机构,(b) Rotating guide-bar mechanism 转动导杆机构,(c) Crank and oscillating block mechanism曲柄摇块机构,(c) Oscillating guide-bar mechanism摆动导杆机构,(d) Translating sliding-rod mechanism移动导杆机构,Taking different links as the frame for slider mechanisms,构件3为机架移动导杆机构,构件4为机架曲柄摇杆机构,构件1为机架双曲柄机构,构件2为机架曲柄摇杆机构,构件3为机架双摇杆机构,构件4为机架曲柄滑块机构,构件1为机架转动导杆机构,构件2为机架曲柄摇块机构、摆动导杆机构,曲柄滑块机构,表31,4.Application of other typical Four-bar Linkages,(1) Applicatio
