平面四杆机构的演化Evolutionofplanarfou

平面四杆机构的演化Evolutionofplanarfourbarmechanisms主讲人：周会娜基本型式一一铰链四杆机构Basictype-hingefourbarmechanism目录CONTENTS1234曲柄滑块机构IntroductiontoMechanicalDrawing偏心轮机构Drawingformatofmechanicaldrawings导杆机构FrameofMechanicalDrawing定块机构Writingfontsformechanicaldrawings5摇块机构Thesignificanceoflearningmechanicaldrawing1曲柄滑块机构CrankslidermechanismONE曲柄摇杆机构crank-rockermechanism一、曲柄滑块机构Crankslidermechanism当AB杆能整周回转成为曲柄时，该机构称为曲柄滑块机构;否则该机构称为摆杆滑块机构。WhentheABrodcanrotateallthewaytobecomeacrank,thismechanismiscalledacrankslidermechanism;Otherwise,themechanismiscalledapendulumslidermechanism.曲柄摇杆机构Crankrockermechanism一、曲柄滑块机构Crankslidermechanism对心曲柄滑块机构centricslider-crankmechanism偏置曲柄滑块机构offsetslider-crankmechanism一、曲柄滑块机构Crankslidermechanism对心曲柄滑块机构:曲柄回转中心与滑块移动导路中心线无偏距。Centeredcrankslidermechanism:Thereisnooffsetbetweenthecrankrotationcenterandthecenterlineoftheslidermovementguide.一、曲柄滑块机构Crankslidermechanism偏置曲柄滑块机构:曲柄回转中心至滑块移动导路中心线存在垂直距离e(即有偏距)Biascrankslidermechanism:Thereisaverticaldistancee(i.e.offset)betweenthecrankrotationcenterandthecenterlineoftheslidermovementpath一、曲柄滑块机构Crankslidermechanism偏置曲柄滑块机构offsetslider-crankmechanism偏心的距离e称作偏心距。Thedistanceeofeccentricityiscalledeccentricity.滑块的两个极限位置之间的距离称为机构的行程H。ThedistancebetweenthetwolimitpositionsoftheslideriscalledthetravelHofthemechanism.一、曲柄滑块机构Crankslidermechanism曲柄滑块机构的运动特性Kinematiccharacteristicsofcrankslidermechanism1.急回运动和行程速比系数1.Quickreturnmotionandtravelspeedratiocoefficient偏置曲柄滑块机构offsetslider-crankmechanism一、曲柄滑块机构CrankslidermechanismHΦ1>φ2

t1>t2V2>v1工作行程空回行程滑块行程SlidestrokeHH曲柄转速Crankspeedωω曲柄转角crankangleφ1=180°+θφ2=180°-θ运动时间Exercisetimet1t2滑块的平均速度TheaveragespeedofthesliderV1V2一、曲柄滑块机构Crankslidermechanism行程速比系数:Travelspeedratiocoefficient：一、曲柄滑块机构Crankslidermechanism偏心曲柄滑块机构有极位夹角θ时，就有急回运动特性，而且θ角越大K值就越大，机构的急回特性就越显著。EccentriccrankslidermechanismwithextremepositionangleθAtthistime,thereisarapidreturnmotioncharacteristic,andθThelargertheangle,thegreatertheKvalue,andthemoresignificantthequickreturncharacteristicofthemechanism.一、曲柄滑块机构Crankslidermechanism对心曲柄滑块机构有急回特性吗?Doesthecentercrankslidermechanismhaveaquickreturncharacteristic?极位夹角θ=0，行程速比系数K=1。Polarangleθ=0,travelspeedratiocoefficientK=1.Thecenteringcrankslidermechanismhasnoreturncharacteristic对心曲柄滑块机构无急回特性。一、曲柄滑块机构Crankslidermechanism曲柄滑块机构的运动特性Kinematiccharacteristicsofcrankslidermechanism死点位置dead-centerposition2.死点Deadpoint一、曲柄滑块机构Crankslidermechanism当滑块为主动件，存在两个死点位置。Whenthesliderisanactivecomponent,therearetwodeadcenterpositions.连杆和曲柄共线时，过铰链中心A的力，对A点不产生力矩，不能使曲柄转动。Whentheconnectingrodandthecrankarecollinear,theforcepassingthroughthecenterAofthehingedoesnotgeneratetorqueatpointAandcannotcausethecranktorotate.死点位置dead-centerposition一、曲柄滑块机构Crankslidermechanism曲柄滑块机构的应用：Theapplicationofcrankslidermechanism内燃机气缸一一对心曲柄滑块机构Internalcombustionenginecylinder--centricslider-crankmechanism一、曲柄滑块机构Crankslidermechanism曲柄滑块机构的应用Theapplicationofcrankslidermechanism自动送料装置一一偏心曲柄滑块机构Automaticfeedingdevice-eccentriccrankslidermechanism一、曲柄滑块机构Crankslidermechanism2偏心轮机构EccentricwheelmechanismTWO二、偏心轮机构Eccentricwheelmechanism曲柄摇杆机构Crank-rockermechanism工程中常将转动副的半径扩大至超过曲柄长度变成圆盘，此偏心圆盘称为偏心轮。曲柄为偏心轮结构的连杆机构称为偏心轮机构。Inengineering,theradiusoftherotatingpairisoftenexpandedbeyondthelengthofthecranktobecomeadisc,whichiscalledaneccentricwheel.Theconnectingrodmechanismwithaneccentricwheelstructureiscalledaneccentricwheelmechanism二、偏心轮机构Eccentricwheelmechanism二、偏心轮机构Eccentricwheelmechanism曲柄摇杆机构的演化一一偏心轮机构Theevolutionofcrankrockermechanism-eccentricwheelmechanism二、偏心轮机构Eccentricwheelmechanism偏心轮机构的应用Theapplicationofeccentricwheelmechanism剪床shearingmachine机构的演化方法:选择机构中不同的构件为机架。Mechanismevolutionmethod:Selectdifferentcomponentsinthemechanismasframes.(a)对心曲柄滑块机构(b)导杆机构(c)摇块机构(d)定块机构centricslider-crankmechanismguide-barmechanismShakermechanismBlockfixingmechanism二、偏心轮机构Eccentricwheelmechanism3导杆机构GuiderodmechanismTHREE三、导杆机构Guiderodmechanism取曲柄滑块机构中原曲柄为机架构成导杆机构。原曲柄2为主动件，若I3<I2，导杆1作往复摆动，称为摆动导杆机构。Taketheoriginalcrankofthecrankslidermechanismastheframetoformaguiderodmechanism.Theoriginalcrank2isanactivecomponent.IfI3<I2,theguiderod1oscillatesbackandforth,whichiscalledaswingingguiderodmechanism摆动导杆机构oscillatingguide-barmechanism三、导杆机构Guiderodmechanism取曲柄滑块机构中原曲柄为机架构成导杆机构。Taketheoriginalcrankofthecrankslidermechanismastheframetoformaguiderodmechanism.原连杆3为主动件，若I3≥I2，导杆1作整周运动，称为转动导杆机构。Theoriginalconnectingrod3isanactivecomponent.IfI3≥I2,guiderod1movesinafullcircle,whichiscalledarotatingguiderodmechanism.摆动导杆机构oscillatingguide-barmechanism4定块机构FixedblockmechanismFOUR曲柄滑块机构中，如取滑块为机架，则该机构演化成定块机构。Inthecrankslidermechanism,iftheslideristakenasaframe,themechanismevolvesintoafixedblockmechanism.四、定块机构Fixedblockmechanism定块机构Fixedblockmechanism手压抽水机Handpresswaterpump5摇块机构Shak