Hydraulic control systemWord文件下载.docx

Hydraulic control systemWord文件下载.docx

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Ahydrauliccontrolsystemisprovidedforuseinaforklifttruckhavinganengine,asteeringcylinder,aliftcylinder,atiltcylinder,asteeringpumprotatablydrivenbytheengineforproducingasteeringfluidunderpressuretoactuatethesteeringcylinderandamainpumpforgeneratingaworkingfluidunderpressuretoactuatetheliftandtiltcylinders.Thesystemincludesasteeringcontrolvalveunitforchangingfiowpathofthesteeringfiuidtocontrolmovementofthesteeringcylinder,apriorityvalvelyingbetweenthesteeringpumpandthesteeringcontrolvalveunitforsupplyingthesteeringcontrolvalveunit.withacontrolledamountofthesteeringfluid,amaincontrolvalveunitselectivelyconnectedtothemainpumpandadaptedtocontrolmovementoftheliftandtiltcylindersandastallvalveremaining,whentheengineisrotatingatnogreaterthanapreselectedrpm,inafirstpositioninwhichtheworkingfiuidisbypassedtotheprior:

ityvalveand,whentheengineisrotatingatgreaterthanthepreselectedrpm,shiftedtoasecondpositioninwhichtheworkingfiuidisfedtothemaincontrolvalveunit.

FIG.1

FIG.2

FIG.3

Hydrauliccontrolsystemforuseinaforklifttruck

Fieldoftheinvention

Thepresentinventionpertainsgenerallytoaforklifttruckandmoreparticularlytoahydrauliccontrolsystemfortheforklifttruckwherebysuchfluidpressureactuatorsassteeringcylinder,liftcylinderandtiltcylindercanbecontrolledtoefiectivelyperformthetasksassignedthereto.

Descriptionofthepriorart

Aswidelyknownintheart,theconventionalhydrauliccontrolsystemforthoseforklifttruckshavingaloadcapacityofmorethan5tonsisdesignedtoemployasteernngpumpfortheproductionofasteeringfluidunderpressurewhichistobeusedinasteeringcontrolpartandamainpumpforthegenerationofaworkingfluidunderpressurewhichistobeutilizedinawork/ngcontrolpart.Thesteeringcontrolpartincludesasteeringcylinder,asteeringcontroaivalveunitadaptedtochangeflowpathofthesteeringfluidtocontrolactuationofthesteeringcylinder,dependingontheturningdirectionandspeedofasteeringwheel,andapriorityvalveinstalledintermediatethesteeringp:

~n~o~c:

thesteeringcontrolvalveunitforenablingaconstantofthesteeringfluidtobedeliveredfromthesteeringpumptothesteeringcontrolvalveunit.

Theworkingcontrolpartincludes,amongotherthings,aliftcylinder,atiltcylinderandamaincontrolvalveunitadaptedtoindependentlycontrolthemovementoftandtiltcylindersbyuseoftheworkingfluidsuppliedfromthemainpump.Moreover,astallvalveisusuallyemployedinthehydrauliccontrolsystemtoprevent"

death"

orshutoffofanengineduetotheoverloadthatmightbeappliedtothemainpumpastheliftcylinderand/orthetiltcylirderand/orthetiltcylinderisactuatedatalowenginerpmrange.

IllustratedinFIG..1isatypicalhydrauliccontrolsystemwhichhasbeenputintopracticalusetocontrolmovementofvariousactuatorsinaforklifttruck.Thehydrauliccontrolsystemisprovidedwithasmallcapacitysteeringpump10andalargecapacitymainpump12,bothofwhicharerotatinglydrivenbymeansofanengine14toproduce,respectively,steeringfluidandworkingfluidunderpressure.Thesteeringpump10isinfluidcommunicationwithasteeringcylinder16bywayofapriorityvalve18andasteeringcontrolvalveunit20.Inparallelwiththepriority

valve18,asteeringreliefvalve22isconnectedtothesteeringpump10inordertodrainthesteeringfluidtoareservoir24whenthepressureofthesteeringfluidincreasesbeyondapermissibleextent.Themainpump12isinfluidcommunicationwithaliftcylinder26andatiltcylinder28bywayofastallvalve30andamaincontrolvalveunit32.Inparalleltothemaincontrolvalveunit32,astallreliefvalve34isconnectedtothestallvalve30todraintheworkingfiuidatafirstreliefpressure.Themaincontrolvalveunit32includesaliftcylindercontrolvalve36,atiltcylindercontrolvalve38andamainreliefvalve40designedtodraintheworkingfluidatasecondreliefpressurehigherthanthefirstreliefpressure.

Withthehydrauliccontrolsystemconstructedasabove,themainpump12willcontinuetoproduceaworkingfluidoflowerpressureaslongastheengine14isrotatingatalowspeed,e.g.,lessthan1000rpm.Inthisstate,thestallvalve30remainsinafirstoperativepositionasshowninFIG.1.toputthemaincontrolvalveunit32incommunicationwiththestallreliefvalve34aswellasthemainpump12.Ifeithertheliftcylindercontrolvalve36orthetiltcylindercontrolvalve38inthemaincontrolvalveunit32isshiftedfromaneutralpositionasdepictedinFIG.1.toanoperativeposition,theworkingfluidwillbefedtotheliftcylinder26orthetiltcylinder28,resultinginanabruptincreaseintheworkingfluidpressure.Thisloadpressurewillbetransmittedbacktothestallreliefvalve34viathemaincontrolvalve

unit32andthestallvalve30.Thusthest,allreliefvalve34willdraintheworkingfluidtothereservoir24tomakesureiothattheloadpressureshouldnotbedeliveredtothemainpump12,whichwouldotherwisecausetheengine14to"

stall"

orstop.

Intheeventthattheenginerpmisincreasedto,e.g.,morethan1000,themainpump12willproduceaworkingfluidofhigherpressuretohavethestallvalve30automaticallyshiftedtoasecondoperativepositionnot.showninFIG.1,therebydisconnectingthestallreliefvalve34fromthemainpump12andthemaincontrolvalveunit32.Inthisstate,theloadpressureactingontheliftcylinder260rthetiltcylinder28willnotbedrainedunlessitreachesthesecondreliefpressureofthemainreliefvalve40.Sincetheengine14isrotatingatmorethan1000rpm,itwillnotbesubjectedtoanystallingevenifthehigherloadpressureisdeliveredbacktothemainpump12.

Meanwhile,thesteeringfluiddischargedinthesteeringpump10willbesuppliedtothesteeringcontrolvalveunit20viathepnontyvalve18thatcanactasapressurecompensatorvalvefor,regardlessofthedischargefluidvolumeofthesteeringpump10,supplyingacontrolledvolumeofthesteeringfluidtothesteeringcontrolvalveunit20.ThefluidvolumeQrtobefedtothesteeringcontrolvalveunit20dependsonorvarieswiththenominalfluidquantityqm（cc/rev）dischargedbythesteeringcontrolvalveunit20andthemaximumturningspeedNh（rpm）ofasteeringwheel,asgivenbythefollowingequation:

[I]

And,thethresholdfluidquantityQpdischargedbythesteeringpump10shouldbegreatenoughtoassureastablesteeringoperationevenwhentheengine14isrotatingatalow,idlerpm,asexpressedbythefollowingequation:

[II]

wherein（Ne）ldenotestheidlerpmoftheengine,qm2thenominalfluidquantityitdischargedbythesteer:

ingcontrolvalveunitandVthevolumetricemciencyofthesteeringpump.

Analyzingthecorrelationofequations[I]and[II]revealsthatthethresholdfluidquantityQPoughttobeincreasedabovetherequiredfluidvolumeQrinresponsetotheenginerpmincrease.Forthatreason,thesurplusfluidquantityproducedbythesteeringpump10hastobedrainedtothereservoir24viathesteeringreliefvalve22,thusdeterioratingtheefficiencyofthehydrauliccontrolsystemandhencethefueleconomyoftheengine.

Summaryoftheinvention

Accordingly,itisanobjectoftheinventiontoprovideahydrauliccontrolsystemforuseinaforklifttruckthatenablestheworkingfluidproducedbyamainpumptobeusedforthesteeringpurposeatalowenginerpm,therebyminimizingthefluiddischargequantityofasteeringpumpandeconomizingoperationofthesystem.

因此，这个用于叉车提供液压控制系统的发明的一个目的是，使引导转动的主泵产生的工作流能够低速运转，能够最小化转向泵的流体排放量和使整个系统的运行经济有效。

Anotherobjectoftheinventionistoprovideahydrauliccontrolsystemforuseinaforklifttruckthatcaneliminatetheneedforasteeringreliefvalvetopermitlowercostandlesscomplexityofthesystem.

这个用于叉车提供液压控制系统的发明的另一个目的是，可以消除转向安全阀的需求以降低整个系统的成本和复杂性。

Withtheseobjectsinview,thepresentinventionprovidesahydrauliccontrolsystemforuseinaforklifttruckhavinganengine,asteeringcylinder,aliftcylinder,atiltcylinders,comprising:

asteeringpumprotatablydrivenbytheengineforproducingasteeringfluidunderpressuretoactuatethesteeringcylinderandamainpumpforgeneratingaworkingfluidunderpressuretoactuatetheliftandtiltcylinders,comprising:

asteeringcontrolvalveunitforchangingflowpat.hoftheio

steeringfluidtocontrolmovementofthesteeringcylinder;

apriorityvalvelyingbetweenthesteeringpumpandthesteeringcontrolvalveunitforsupplyingthesteeringcontrolvalveunitwithacontrolledamountofthesteeringfluid;

amaincontrolvalveunitselectivelyconnectedtothemain15pumpandadaptedtocontrolmovementoftheliftandtiltcylinders;

andastallvalveremaining,whentheengineisrotatingatnogreaterthanapreselectedrpm,inafirstpositioninwhichtheworkingfluidisbypassedtothepriorityvalveand,whentheengineisrotatingatgreaterthanthepreselectcdrpm,shiftedtoasecondpositioninwhichtheworkingfluidisfedtothemaincontrolvalveunit.

Briefdescriptionofthedrawing

Theaboveandotherobjects,features,advantagesoftheinventionwillbecomeapparentformareviewofthefollowingdetaileddescriptionofthepreferredembodimenttakeninconjunctionwiththeaccompanyingdrawings,inwhich:

FIG.1isafiuidpressurecircuit