机械设计专业毕业设计文献翻译履带牵引装置的液压传动.pdf

Hydrostaticdriveforcrawlers:

Somedesignadvantages

Hydrostaticoperationofvehiclessuchasdozersandloadersimplies

useofinenginetooperateahydraulicpumporpumps.Highpressure

hosesareusedtotransmitthefluidpressureandflowtoseparatedrive

motorswhichcanbelocatedsomedistancefromengineandpump.The

enginecanberunatitsmostefficientconditionswithareversible,

variableswashplatepump.Thehydraulicmotorscanalsomakeuseof

variableswashplates,simplifyingbothhydraulicdesigns.Onlythe

designadvantagesofsuchasystemarecoveredhere,thoughservice

procedures,lifeexpectancy,andoperatorsallcanbenefitfromother

aspectsofsuchdrives.

Amajordesignobjectiveintheconstructionequipment

manufacturingbusinesssincethe1960shasbeenmoreefficientuseof

installedhorsepower.Lowefficiencymeansenergywastedasheatwhich,

initsturn,usuallyrequiresextrapowertodrivefansandmaintain

temperature.Themoreinefficientthemachine,thehotteritgets,soheat

servesasameasuringscaleforoverallefficiency.

Withinamachine,enginehorsepoweristransformedintoforce(psi)

andspeed(gal/mm).Forpurposesofcomparingdifferentsystemsone

canusetheexpression:

Enginehp∝ForcexSpeedwhereforcemeansdrawbarpull(lbs)

andspeedmeanstravelspeed(mph).

Sinceallmachineshaveinternallosses,theidealforce/speed

hyperbolacannotbeachieved.However,themoreefficient,theclosera

machinesystemapproachestheidealcurve,andthemoreworkitcan

producefromagivenamountofinstalledenginehorsepower(Fig.1).

Toappreciatetheefficiencyofahydrostaticdrive,itisnecessaryto

lookatthepowerutilizationofconventionaldrives

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