文献翻译认识曲柄摇臂机构设计的最优传动方法Word下载.docx
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Keywords:
Crank-and-rockermechanism,Optimaltransmissionangle,Coefficientoftravelspeedvariation
INTRODUCTION
Byconventionalmethodofthecrank-and-rockerdesign,itisverydifficulttorealizetheoptimalcombinationbetweenthevariousparametersforoptimaltransmission.Thefigure-tabledesignmethodintroducedinthispapercanhelpachievethisgoal.Withgivenconditions,wecan,byonlyconsultingthedesigningfiguresandtables,gettherelationsbetweeneveryparameterandanotherofthedesignedcrank-and-rockermechanism.Thustheoptimaltransmissioncanberealized.
Theconcerneddesigningtheoryandmethod,aswellastherealcasesofitsapplicationwillbeintroducedlaterrespectively.
1ESTABLISHMENTOFDIAGRAMFOROPTIMALTRANSMISSIONDESIGN
Itisalwaysoneofthemostimportantindexesthatdesignerspursuetoimprovetheefficiencyandpropertyofthetransmission.Thecrank-and-rockermechanismiswidelyusedinthemechanicaltransmission.Howtoimproveworkabilityandreduceunnecessarypowerlossesisdirectlyrelatedtothecoefficientoftravelspeedvariation,theoscillatingangleoftherockerandtheratioofthecrankandrocker.Thereasonablecombinationoftheseparameterstakesanimportanteffectontheefficiencyandpropertyofthemechanism,whichmainlyindicatesintheevaluationoftheminimumtransmissionangle.
Theaimrealizingtheoptimaltransmissionofthemechanismishowtofindthemaximumoftheminimumtransmissionangle.Thedesignparametersarereasonablycombinedbythemethodoflesseningconstraintsgraduallyandoptimizingseparately.Consequently,thecompleteconstraintfieldrealizingtheoptimaltransmissionisestablished.
Thefollowingstepsaretakenintheusualdesignmethod.Firstly,theinitialvaluesofthelengthofrocker
andtheoscillatingangleofrocker
aregiven.Thenthevalueofthecoefficientoftravelspeedvariation
ischoseninthepermittedrange.Meanwhile,thecoordinateofthefixedhingeofcrank
possiblyrealizediscalculatedcorrespondingtovalue
.
1.1Lengthofbarsofcrankandrockermechanism
AsshowninFig.1,leftarc
isthepermittedfieldofpoint
.Thecoordinatesofpoint
arechosenbysmallstepfrompoint
topoint
Thecoordinatesofpoint
are
(1)
(2)
where
thestep,isincreasedbysmallincrementwithinrange(0,
).Ifthesmallerthechosenstepis,thehigherthecomputationalprecisionwillbe.
istheradiusofthedesigncircle.
isthedistancefrom
to
(3)
Calculatingthelengthofarc
and
thelengthofthebarsofthemechanismcorrespondingtopoint
isobtained[1,2].
1.2Minimumtransmissionangle
Minimumtransmissionangle
(seeFig.2)isdeterminedbytheequations[3]
(4)
(5)
(6)
where
——Lengthofcrank(mm)
——Lengthofconnectingbar(mm)
——Lengthofrocker(mm)
——Lengthofmachineframe(mm)
Firstly,wechooseminimumcomparing
with
.Andthenwerecordallvaluesof
greaterthanorequalto
andchoosethemaximumofthem.
Secondly,wefindthemaximumof
correspondingtoanyoscillatingangle
whichischosenbysmallstepinthepermittedrange(maximumof
isdifferentoscillatingangle
andthecoefficientoftravelspeedvariation
).
Finally,wechangethelengthofrocker
bysmallstepsimilarly.Thuswemayobtainthemaximumof
correspondingtothedifferentlengthofbars,differentoscillatingangle
Fig.3isaccomplishedfromTableforthepurposeofdiagramdesign.
Itisworthpointingoutthatwhateverthelengthofrocker
isevaluated,thelocationthatthemaximumof
arisesisonlyrelatedtotheratioofthelengthofrockerandthelengthofmachineframe
/
whileindependentof
2DESIGNMETHOD
2.1Realizingtheoptimaltransmissiondesigngiventhecoefficientoft