1、Chapter 3 Planar Linkages Mechanisms and its Design (平面連桿機(jī)構(gòu)及其設(shè)計(jì)),Questions： 1、What is Condition for having a crank (Grashof Criterion) in Four-bar Linkages Chain(鉸鏈四桿運(yùn)動(dòng)鏈中，轉(zhuǎn)動(dòng)副為整轉(zhuǎn)副的充要條件是什么?) 2、What is quick return characteristics of mechanisms(什么是機(jī)構(gòu)的急回特性)？ 3、How to avoid the dead-point position(如何克服死點(diǎn)

2、位置)？,Important contents (重點(diǎn)掌握的內(nèi)容)： 1、Types of Four-bar Linkages (鉸鏈四桿機(jī)構(gòu)類型判斷) 2、The equation of coefficient of travel speed variation and its application(行程速比系數(shù)公式及應(yīng)用) 3、Design of Planar Linkage Mechanisms(平面四桿機(jī)構(gòu)運(yùn)動(dòng)設(shè)計(jì)),Study object: Planar Linkages Mechanism,What is the planar linkages mechanisms (什么是平

3、面連桿機(jī)構(gòu))？,The mechanisms are composed of lower pairs and links(由連桿和低副聯(lián)結(jié)而成的機(jī)構(gòu))。 It is lower-pair mechnisms(或稱低副機(jī)構(gòu))。,Crank-rocker mechanism,Ellipsograph mechanism 橢圓規(guī)機(jī)構(gòu),Crank-slider mechanism,Crank Press 沖床,Planer刨床,Gear planer插齒機(jī),All above it application. What is the characteristics of planar linkages

4、mechanism?,3-1Characteristic of linkage mechanisms and its design (連桿機(jī)構(gòu)的特點(diǎn)及其設(shè)計(jì)的基本問題),Planar linkage mechanisms平面連桿機(jī)構(gòu)。,Planar linkage mechanism is popular in industrial application. 平面連桿機(jī)構(gòu)有諸多優(yōu)點(diǎn)被廣泛應(yīng)用。,1. Types of linkage mechanisms(連桿機(jī)構(gòu)的分類)：,（1）According to relative motion of links (根據(jù)其構(gòu)件間的相對(duì)運(yùn)動(dòng)分類)。,Sp

5、atial linkage mechanisms空間連桿機(jī)構(gòu)。,Four-bar linkages 四桿機(jī)構(gòu)。,（2） According to number of links (根據(jù)構(gòu)件的數(shù)目分類)。,Five-bar linkages五桿機(jī)構(gòu)。,.桿機(jī)構(gòu)。,一、Characteristics of mechanisms,2. Advantages of planar linkage mechanisms (平面連桿機(jī)構(gòu)的主要優(yōu)點(diǎn))：,（2） The contact pressure stress is lower,and it is easy to manufacture. (低副不易磨損

6、而又易于加工)。,（1） It can perform many motion (能夠?qū)崿F(xiàn)多種運(yùn)動(dòng)軌跡曲線和運(yùn)動(dòng)規(guī)律)；,（3）Structure is simple(幾何封閉，結(jié)構(gòu)簡(jiǎn)單)。,3-1 Character of linkage mechanisms and its design (連桿機(jī)構(gòu)的特點(diǎn)及其設(shè)計(jì)的基本問題),3. Disadvantages of planar linkage mechanisms (平面連桿機(jī)構(gòu)的主要缺點(diǎn))：,（1）Inertia force and inertia moment(慣性力及慣性力矩)。,（2）Approximately achieve a

7、nticipated motion (近似實(shí)現(xiàn)預(yù)期的運(yùn)動(dòng)規(guī)律，設(shè)計(jì)方法復(fù)雜)。,（3）Cumulative error(造成累計(jì)誤差)。,4. Application(平面連桿機(jī)構(gòu)的應(yīng)用)：,light industrial machinery, agricultural machinery (輕工機(jī)械、農(nóng)業(yè)機(jī)械等)。,（連桿機(jī)構(gòu)作變速運(yùn)動(dòng)的構(gòu)件引起振動(dòng)和噪聲的主要原因，如紡織廠，噪音污染十分嚴(yán)重，現(xiàn)在有所改善，但機(jī)構(gòu)決定不可避免）,5. Development trend發(fā)展趨勢(shì)：,Computer aided design(計(jì)算機(jī)輔助設(shè)計(jì)是一大趨勢(shì))。,3-1 Character of l

8、inkage mechanisms and its design (連桿機(jī)構(gòu)的特點(diǎn)及其設(shè)計(jì)的基本問題),1. Implement anticipated motion (實(shí)現(xiàn)預(yù)期的運(yùn)動(dòng)規(guī)律),Molding machine 造型機(jī)的翻轉(zhuǎn)機(jī)構(gòu),3-1 Character of linkage mechanisms and its design (連桿機(jī)構(gòu)的特點(diǎn)及其設(shè)計(jì)的基本問題),Transverse planing machine牛頭刨主體機(jī)構(gòu),二、Basic Section of Design 設(shè)計(jì)的基本問題,2. Implement anticipated moving track 實(shí)現(xiàn)預(yù)

9、期的運(yùn)動(dòng)軌跡,Crane起重機(jī),Blender攪拌機(jī),3-1 Character of linkage mechanisms and its design (連桿機(jī)構(gòu)的特點(diǎn)及其設(shè)計(jì)的基本問題),二、Basic Section of Design 設(shè)計(jì)的基本問題,Four-bar Linkages is most popular in planar linkage mechanisms. 平面連桿機(jī)構(gòu)中結(jié)構(gòu)最簡(jiǎn)單、應(yīng)用最廣的，是四桿機(jī)構(gòu)!,3-2 Types of Four-bar Linkages and its evolution 平面 四桿機(jī)構(gòu)的基本形式及其演變,一、Four-bar Li

10、nkages平面四桿機(jī)構(gòu)的基本形式-鉸鏈四桿機(jī)構(gòu),Slide link 連架桿,Frame機(jī)架,Slide link 連架桿,Coupler連桿,能繞其軸線轉(zhuǎn)360的。,僅能繞其軸線作往復(fù)擺動(dòng)的。,Crank曲柄:,Rocker搖桿:,2.Composition 組成,All pairs are revolute pairs in a four-bar mechanisms 所有運(yùn)動(dòng)副全為轉(zhuǎn)動(dòng)副的四桿機(jī)構(gòu)。,1. Definition：,Frame機(jī)架：固定架。,做平面運(yùn)動(dòng)的構(gòu)件。,Coupler連桿:,連架桿,According to two slide links, types of Fo

11、ur-bar linkages are as following:按照兩連架桿的運(yùn)動(dòng)形式的不同,可將鉸鏈四桿機(jī)構(gòu)分為：,Crank-rocker mechanism曲柄搖桿機(jī)構(gòu),Double-crank mechanisms雙曲柄機(jī)構(gòu),Double-rocker mechanisms雙搖桿機(jī)構(gòu),一般曲柄為原動(dòng)件.P364破碎機(jī)、縫紉機(jī),3.Types分類,(1) Application of Crank-rocker Mechanisms 曲柄搖桿應(yīng)用舉例,Blender攪拌機(jī),Device for training legs下肢力量訓(xùn)練器,4. Application應(yīng)用,Radar sca

12、nning aerial雷達(dá)掃描天線,Fly shear飛剪機(jī)構(gòu),Sewing machine縫紉機(jī),(2) Application of Double-crank Mechanisms雙曲柄應(yīng)用舉例,Train wheel 機(jī)車車輪,Unbalanced-throwscreen慣性篩,(3) Application of Double-rocker Mechanisms雙搖桿應(yīng)用舉例,Aircraft landing gear飛機(jī)起落架,A,D,地面,All above are basic definition, composition, types and application of F

13、our-bar Linkages.,二、 Evolution of Four-bar Linkages 平面四桿機(jī)構(gòu)的演化,Replacing a revolute pair with a sliding pair 轉(zhuǎn)動(dòng)副轉(zhuǎn)化成移動(dòng)副的演化,crank and translating guide-bar mechanism 曲柄移動(dòng)導(dǎo)桿機(jī)構(gòu),in-line(對(duì)心) slider-crank mechanism,eccentric (or offset)(偏置) slider-crank mechanism,對(duì)心曲柄滑塊機(jī)構(gòu),偏置曲柄滑塊機(jī)構(gòu),曲柄滑塊機(jī)構(gòu)（對(duì)心）,曲柄當(dāng)滑塊機(jī)構(gòu)（偏心）,Ecc

14、entric (or offset)(偏置) slider-crank mechanism,In-line(對(duì)心) slider-crank mechanism,曲柄滑塊機(jī)構(gòu) Crank-slide mechanisms,2. Enlarging(擴(kuò)大) a revolute pair 擴(kuò)大回轉(zhuǎn)副,Evolution 演化：,偏心輪機(jī)構(gòu) Eccentric mechanism,曲柄滑塊機(jī)構(gòu) Crank-slide mechanisms,2. Enlarging(擴(kuò)大) a revolute pair 擴(kuò)大回轉(zhuǎn)副,Evolution 演化：,偏心輪機(jī)構(gòu) Eccentric mechanism,E

15、ccentric mechanism 偏心輪機(jī)構(gòu),Application：,Advantages：,High strength, high rigidity, easy to make. 強(qiáng)度高，剛度高，且便于加工制造。,Transfer big force. 用于傳遞較大力場(chǎng)合。 如破碎機(jī)、沖床、剪床、內(nèi)燃機(jī)等。,3. Taking different links as the frame取不同構(gòu)件為機(jī)架,Crank-rocker mechanism,Double-crank Mechanisms,Double rocker Mechanisms,由鉸鏈四桿機(jī)構(gòu)動(dòng)畫知取不同構(gòu)件為機(jī)架各構(gòu)件間

16、的相對(duì)運(yùn)動(dòng)關(guān)系不變，得到四種機(jī)構(gòu),曲柄搖桿機(jī)構(gòu),(b) Rotating guide-bar mechanism 轉(zhuǎn)動(dòng)導(dǎo)桿機(jī)構(gòu),(c) Crank and oscillating block mechanism曲柄搖塊機(jī)構(gòu),(c) Oscillating guide-bar mechanism擺動(dòng)導(dǎo)桿機(jī)構(gòu),(d) Translating sliding-rodmechanism移動(dòng)導(dǎo)桿機(jī)構(gòu),Taking different links as the frame for slider mechanisms,構(gòu)件3為機(jī)架移動(dòng)導(dǎo)桿機(jī)構(gòu),構(gòu)件4為機(jī)架曲柄搖桿機(jī)構(gòu),構(gòu)件1為機(jī)架雙曲柄機(jī)構(gòu),構(gòu)件2為機(jī)架曲

17、柄搖桿機(jī)構(gòu),構(gòu)件3為機(jī)架雙搖桿機(jī)構(gòu),構(gòu)件4為機(jī)架曲柄滑塊機(jī)構(gòu),構(gòu)件1為機(jī)架轉(zhuǎn)動(dòng)導(dǎo)桿機(jī)構(gòu),構(gòu)件2為機(jī)架曲柄搖塊機(jī)構(gòu)、擺動(dòng)導(dǎo)桿機(jī)構(gòu),曲柄滑塊機(jī)構(gòu),表31,4.Application of other typical Four-bar Linkages,(1) Applications of Crank-slider Mechanism:Internal combustion engine（曲柄滑塊機(jī)構(gòu)）,(2) The small planer(刨床) is one of the applications of Rotating Guide-bar Mechanism(轉(zhuǎn)動(dòng)導(dǎo)桿機(jī)構(gòu)).,4.App

18、lication of other typical Four-bar Linkages,(3) The applications of the Oscillating Guide-bar Mechanism（擺動(dòng)導(dǎo)桿機(jī)構(gòu)）.,4.Application of other typical Four-bar Linkages,(4) The applications of the Crank and Oscillating Block Mechanism （曲柄搖塊機(jī)構(gòu)）,4.Application of other typical Four-bar Linkages,(5) Hand-opera

19、ted well(井) pump(泵) mechanism is one of applications of the Translating Sliding-rod Mechanism（移動(dòng)導(dǎo)桿機(jī)構(gòu)）.,4.Application of other typical Four-bar Linkages,All above are composition and evolution of Four-bar linkages. What is its Characteristics?,3-3Character of Four-bar linkages鉸鏈四桿工作特性,1. Necessary an

20、d sufficient condition（鉸鏈四桿運(yùn)動(dòng)連中轉(zhuǎn)動(dòng)副為整轉(zhuǎn)副的充要條件）,一、 Necessary and sufficient condition of revolute being fully rotating revolute in Four-bar linkages Chain（轉(zhuǎn)動(dòng)副為整轉(zhuǎn)副的充分必要條件）,要使AB成為曲柄，則拆副后 AB上的點(diǎn)B應(yīng)在r1與 r2圍成的環(huán) 面內(nèi)運(yùn)動(dòng)。,即使AB轉(zhuǎn)到與機(jī)架共線的 兩位置在環(huán)面內(nèi)。其條件：,要使AB成為曲柄，必須滿足以上條件,由(1)及（2a ）、(2b)可得,當(dāng)da時(shí)，式（2）變?yōu)?(bc),(c b),(2b),（2a

21、 ）,(bc),(c b),要使AB成為曲柄，必須滿足條件,由(1)及（2a ）、(2b)可知a是最短桿，且最短桿與最長(zhǎng)桿長(zhǎng)度之和小于或等于其余兩桿長(zhǎng)度之和。,（2a ）,(2b),同理當(dāng)a d時(shí)，同樣有,由(1)及（2a ）(2b)可得,(1),由(1)及（2a）、(2b)可知d是最短桿，且最短桿與最長(zhǎng)桿長(zhǎng)度之和小于或等于其余兩桿長(zhǎng)度之和。,One of two links composing the revolute is shortest link and the sum length of the shortest and the longest links must be less

22、than or equal to the sum length of the remaining two links. (組成該轉(zhuǎn)動(dòng)副的兩構(gòu)件中必有一個(gè)構(gòu)件為最短構(gòu)件，且最短構(gòu)件與最長(zhǎng)構(gòu)件長(zhǎng)度之和小于或等于其它兩構(gòu)件長(zhǎng)度之和)。,最短構(gòu)件與最長(zhǎng)構(gòu)件長(zhǎng)度之和小于或等于其它兩構(gòu)件長(zhǎng)度之和 桿長(zhǎng)和條件。,This is called Grashof criterion(準(zhǔn)則) or the Condition for having a crank(曲柄存在條件).,（1）If the sum length of the shortest and the longest links is less t

23、han or equal to the sum length of the remaining two links. 如果最短桿與最長(zhǎng)桿的長(zhǎng)度之和小于或等于其它兩桿 長(zhǎng)度之和 滿足桿長(zhǎng)和條件。,For Four-bar Linkages Mechanism(在鉸鏈四桿機(jī)構(gòu)中)：,以最短桿的相鄰構(gòu)件為機(jī)架，則此機(jī)構(gòu)為以最短桿 為曲柄的曲柄搖桿機(jī)構(gòu)；,Then：,For Four-bar Linkages Mechanism(在鉸鏈四桿機(jī)構(gòu)中)：,可用以下方法來判別鉸鏈四桿機(jī)構(gòu)的基本類型：,2.若機(jī)構(gòu)滿足桿長(zhǎng)之和條件，則,(1) 以最短桿的鄰邊為機(jī)架時(shí)為曲柄搖桿機(jī)構(gòu),(2) 以最短桿為機(jī)架時(shí)為雙曲

24、柄機(jī)構(gòu),(3) 以最短桿的對(duì)邊為機(jī)架時(shí)為雙搖桿機(jī)構(gòu),1.若機(jī)構(gòu)不滿足桿長(zhǎng)之和條件則只能成為雙搖桿機(jī)構(gòu),2. Condition for Slider Mechanisms having a crank 滑塊機(jī)構(gòu)有曲柄的條件,Condition of bar “a” is crank(成為曲柄滑塊機(jī)構(gòu)的條件為)：,（e is offset 其中e偏心距離）,The distance from the crankshaft A to the path of the centre of the revolute C is called the offset (偏置), denoted(標(biāo)為) as

25、e.,3. Condition for Guide-bar Mechanisms having a crank 導(dǎo)桿機(jī)構(gòu)有曲柄的條件,da,二、The coefficient of travel speed variation行程速度變化系數(shù),Analysis of Quick Return Characteristics 急回性能分析(曲柄搖桿機(jī)構(gòu)),When AB and BC on the same line, CD is two limitation position (當(dāng)AB與BC兩次共線時(shí)，輸出件CD處于兩極限位置)。,極位夾角：,Crank acute angle between

26、 the two limited position. 曲柄在搖桿處于兩極限位置時(shí)所夾的銳角(C1AC2)。,Assuming：The rotation speed is a constant 1(曲柄以1等速轉(zhuǎn)動(dòng)),Angular stroke of the rocker擺角：,The angle between two limitation position of rocker 搖桿在兩極限位置間的夾角(C1DC2)。,二、The coefficient of travel speed variation行程速度變化系數(shù),Angle of crank rotating 曲柄轉(zhuǎn)角,Time o

27、f crank AC rotating 對(duì)應(yīng)的時(shí)間,Average speed of point C 搖桿點(diǎn)C的平均速度,),),Apparently,Working stroke,Return stroke,Analysis of Quick Return Characteristics 急回性能分析(曲柄搖桿機(jī)構(gòu)),Quick Return Characteristics and The Coefficient of Travel Speed Variation （急回特性和行程速比系數(shù)),Quick Return Characteristics（急回特性）,Characteristic

28、for the speed of working part during return stroke is bigger than working strokes (機(jī)構(gòu)工作件返回行程速度大于工作行程速度的特性)。,Working stroke：V1 Return stroke：V2,The Coefficient of Travel Speed Variation(行程速比系數(shù))K,The ratio of the faster average speed V2 to the slower one V1. is to express the extend of quick returning

29、表示工作件往復(fù)運(yùn)動(dòng)時(shí)的急回程度.,Then：,The condition of Four-bar linkages having Quick Return Characteristics平面四桿機(jī)構(gòu)具有急回特性的條件：,（1）The speed of driving link is a constant 原動(dòng)件作等速整周轉(zhuǎn)動(dòng)；,（2）Output link move back and forth alternately 輸出件作往復(fù)運(yùn)動(dòng)；,（3）,Effect of Quick Return Characteristics 急回特性的作用,Save space and increase pro

30、ductive efficiency 急回特性可以節(jié)省空間，提高生產(chǎn)率。,2. Crank-slider Mechanisms曲柄滑塊機(jī)構(gòu)中，原動(dòng)件AB以,等速轉(zhuǎn)動(dòng),有急回特性。,3.Crank oscillating guide-bar mechanism 曲柄擺動(dòng)導(dǎo)桿機(jī)構(gòu),有急回特性。,(1)Press Angle: 壓力角：,The transmission angle is the complement of the pressure angle 傳動(dòng)角是壓力角的余角,越小,傳力性能越好。,越大,傳力性能越好。,effective force,no effective force,三、

31、Pressure Angle and Transmission Angle 壓力角和傳動(dòng)角,機(jī)構(gòu)中驅(qū)使輸出件運(yùn)動(dòng)的力的方向線與輸出件上受力點(diǎn)的速度方向線所夾的銳角,(2) Transmission Angle: 傳動(dòng)角 ：,（一）Definition of Pressure Angle and Transmission Angle,Draw pressure angle in the Figure,Examples：,（二）The position of minimum g 平面四桿機(jī)構(gòu)的最小傳動(dòng)角位置,1 . Four-bar Linkage鉸鏈四桿機(jī)構(gòu)中,For Crank-slider

32、Mechanism,當(dāng)曲柄和機(jī)架處于兩共線位置時(shí)，連桿和輸出件的夾角 最小和最大（ ）。,當(dāng)壓力角變化時(shí)影響到有效分力大小，希望壓力角越小越好，傳動(dòng)角越大越好。當(dāng)傳動(dòng)角很小時(shí)，效率會(huì)很低。故限定最小傳動(dòng)角。一個(gè)循環(huán)中，傳動(dòng)角是變化的在哪里最小呢?,一般取40，重載時(shí)50,2. Offset Crank-slider Mechanism AB為主動(dòng)的偏置曲柄滑塊機(jī)構(gòu),只有使偏置方位、曲柄轉(zhuǎn)向、輸出件工作行程方向 正確匹配，方能保證輸出件有急回特性,Maximum pressure angle is at return stroke. 機(jī)構(gòu)的最大壓力角處于輸出件的回程位置。,3. Guide-ba

33、r mechanism AB為主動(dòng)的導(dǎo)桿機(jī)構(gòu),For Guide-bar mechanism AB為主動(dòng)的導(dǎo)桿機(jī)構(gòu),Position of Dead-points： 死點(diǎn)位置：,的機(jī)構(gòu)位置,四、 Position of Dead-points 死點(diǎn)位置,當(dāng)機(jī)構(gòu)處于傳動(dòng)角,The position with Transmission Angle bing zero,FB,vB,Think： Where is the dead-point position for following mechanisms? 下列機(jī)構(gòu)的死點(diǎn)位置在哪里?,How to carry the mechanism through the dead point position? 怎樣使機(jī)構(gòu)通過死點(diǎn)位置?,Flywheel can help mechanism through the dead point position.,Application of dead-point position 死點(diǎn)位置利用,A,D,地面,Aircraft landing gear 飛機(jī)起落架機(jī)構(gòu),Application of dead-point position 死點(diǎn)位置利用,Application