专业英语3.docx

专业英语3.docx

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专业英语3

3.3.1Non-positiveconstantloadsynchromeshunit（Fig.35（a,bandc））

Whenthegearstickisintheneutralpositionthespringloadedballstrappedbetweentheinnerandouterhubareseatedinthecircumferentialgrooveformedacrossthemiddleoftheinternaldogteeth（Fig.35（a））.Asthedriverbeginstoshiftthegearstickintosaytopgear（towardstheleft）,theouterandinnersynchromeshhubsmoveasoneduetotheradialspringloadingoftheballsalongthesplinesformedonthemainshaftuntilthefemaleconeoftheouterhubcontactsthemaleconeofthefirstmotiongear（Fig.35（b））.Whenthepairofconicalfacescontact,frictionaltorquewillbegeneratedduetothecombinationoftheaxialthrustandthedifferenceinrelativespeedofbothinputandoutputshaftmembers.Ifsufficientaxialthrustisappliedtotheouterhub,theballswillbedepressedinwardsagainsttheradialloadingofthesprings.Immediateltheballsarepushedoutoftheirgroove,thechamferededgesoftheouterhub’sinternalteethwillthenbeabletoalignwiththecorrespondingteethspacingonthefirstmotiongear.Bothsetsofteethwillnowbeabletomeshsothattheouterhubcanbemovedintothefullyengagedposition（Fig.35（c））.

Notethebronzefemaleconeinsertfrictionalfaceisnotsmooth,butconsistsofaseriesoftramlinegrooveswhichassistincuttingawaytheoilfilmsothatamuchlargersynchronizingtorquewillbegeneratedtospeeduptheprocess.

3.3.2Positivebaulkringsynchromeshunit（Fig.36（a,bandc））

Thegearboxmainshaftrotatesatpropellorshaftspeedand,withtheclutchdisengaged,thefirstmotionshaftgear,layshaftclustergears,andmainshaftgearsrotatefreely.

Drivetorquewillbetransmittedwhenagearwheelispositivelylockedtothemainshaft.Thisisachievedbymeansoftheoutersynchromeshhubinternalteethwhichslideovertheinnersynchromeshhubsplines（Fig.36（a））untiltheyengagewithdogteethformedontheconstantmeshgearwheelbeingselected.

Whenselectingandengagingaparticulargearratio,thegearstickslidesthesynchromeshouterhubinthedirectionofthechosengear（towardstheleft）.Becausetheshiftplateisheldradiallyoutwardsbythetwoenergizingringtypespringsandtheraisedmiddlehumpoftheplaterestsinthegrooveformedontheinsideofthehub,theendoftheshiftplatecontactsthebaulkingringandpushesittowardsandovertheconicalsurface,formingpartoftheconstantmeshgearwheel（Fig.36（b））.

Thefrictionalgripbetweenthemaleandfemaleconicalmembersofthegearwheelandbaulkingringandthedifferenceinspeedwillcausethebaulkingringtobedraggedaroundrelativetotheinnerhubandshiftplatewithinthelimitsoftheclearancebetweentheshiftplatewidthandthatoftherecessedslotinthebaulkingring.Owingtothedesignedwidthoftheshiftplateslotinthebaulkingring,theteethonthebaulkingringarenowoutofalignmentwiththoseontheouterhubbyapproximatelyhalfatoothwidth,sothatthechamferedfacesoftheteethofthebaulkingringandouterhubbearuponeachother.

Asthebaulkingringisincontactwiththegearconeandtheouterhub,theforceexertedbythedriveronthegearstickpressesthebaulkingringfemaleconehardagainstthemaleconeofthegear.Frictionaltorquebetweenthetwosurfaceswilleventuallycausethesetwomemberstoequalizetheirspeeds.

Untilthistakesplace,fullengagementofthegearandouterhubdogteethispreventedbytheoutofalignmentpositionofthebaulkingringteeth.Whenthegearwheelandmainshafthaveunifiedtheirspeeds,thesynchronizingtorquewillhavefallentozerosothatthebaulkingringisnolongerdraggedoutofalignment.Thereforetheouterhubcannowovercomethebaulkandfollowthroughtomakea

positiveengagementbetweenhubandgear（Fig.36（c））.Itshouldbeunderstoodthatthefunctionoftheshiftplateandspringsistotransmitjustsufficientaxialloadtoensurearapidbringingtogetherofthematingconessothatthebaulkingringdogteethimmediatelymisalignwiththeircorrespondingouterhubteeth.Oncetheconefacescontact,theygeneratetheirownfrictiontorquewhichissufficienttoflickthebaulkingringover,relativetotheouterhub.Thusthechamfersofbothsetsofteethcontactandopposefurtherouterhubaxialmovementtowardsthegeardogteeth.

3.3.3Positivebaulkpinsynebromeshunit（Fig.37（a,b,candd））

Movementoftheselectorforksynchronizingsleevetotheleft（Fig.37（aandb））forcesthefemale（internal）conetomoveintocontactwiththemale（external）coneonthedrivegear.Frictionaltorquewillthensynchronize（unify）theinputandoutputspeeds.Untilspeedequalizationisachieved,thecollarsonthethreethrustpins（onlyoneshown）willbepressedhardintotheenlargedpositionoftheslots（Fig.35（c））inthesynchronizingsleeveowingtothefrictionaldragwhenthespeedsaredissimilar.Undertheseconditions,unlessextremepressureisexerted,thedogteethcannotbecrushedbyforcingthecollarsintothenarrowportionoftheslots.However,whenthespeedsofthesynchromeshhubanddrivegearareequal（synchronized）thecollarstendto¡®float¡¯intheenlargedportionoftheslots,thereisonlythepressureofthespringloadedballstobeovercome.Thecollarswillthenslideeasilyintothenarrowportionoftheslots（Fig.35（d））allowingthesynchronizerhubdogteethtoshiftintomeshwiththedogteethonthedrivinggear.

3.3.4Splitbaulkpinsynebromeshunit.（Fig.38（a,b,candd））

Thesynchronizingassemblyiscomposedoftwothickbronzesynchronizingringswithtaperedfemaleconicalbores,andsituatedbetweenthemisahardenedsteeldrivehubinternallysplinedwithexternaldogteethateachend（Fig.38（a））.Threeshoulderedpins,eachwithagroovearounditscentre,holdthebronzesynchronizingconeringsapart.Alternatingwiththeshoulderedpinsonthesamepitchcirclearediametricallysplitpins,theendsofwhichfitintoblindboresmachinedinthesynchronizingconerings.Thepinhalvesaresprungapart,sothatachamferedgroovearoundthemiddleofeachhalfpinregisterswithachamferedholeinthedrivehub.

Ifthegearboxisintheneutralposition,bothsetsofshoulderedandsplitpinsaresituatedwiththeirgroovesalignedwiththecentraldrivehub（Fig.38（aandb））.

Whenanaxialloadisappliedtothedrivehubbythegearstick,itmovesover（inthiscasetotheleft）untilthesynchronizingringisforcedagainsttheadjacentfirstmotiongearcone.Thefriction（synchronizing）torquegeneratedbetweentherubbingtaperedsurfacesdragsthebronzesynchronizingringrelativetothemainshaftanddrivehubuntilthegroovesintheshoulderedpinsarewedgedagainstthechamferededgesofthedrivehub（Fig.38（c））sothatfurtheraxialmovementisbaulked.

Immediatelytheinputandoutputshaftspeedsaresimilar,thatis,synchronizationhasbeenachieved,thespringsinthesplitpinsareabletoexpandandcentralizetheshoulderedpinsrelativetothechamferedholesinthedrivehub.Thedrivehubcannowrideoutofthegroovesfomedaroundthesplitpins,thuspermittingthedrivehubtoshiftfurtheroveruntiltheinternalandexternaldogteethofbothgearwheelhubmeshandfullyengage（Fig.38（d））.

3.3.5Splitringsynebromeshunit（Fig.3.9（a,b,candd））

Intheneutralpositiontheslidingsleevesitscentrallyoverthedrivehub（Fig.39（a））.Thispermitsthesynchronizingringexpanderbandandthrustblocktofloatwithintheconstraintsoftherecessmachineinthesideofthegearfacingthedrivehub（Fig.39（b））.

Forgearengagementtotakeplace,theslidingsleeveismovedtowardsthegearwheelselected（totheleft）untiltheinsidechamferoftheslidingsleevecontactsthebevelledportionofthesynchronizingring.Asaresult,thesynchronizingringwillbeslightlycompressedandthefrictiongeneratedbetweenthetwomembersthendragsthesynchronizingringroundinthedirectionofwhichevermemberisrotatingfastest,beitthegearordrivenhub.Atthesametime,thethrustblockispulledroundsothatitappliesaloadtooneendoftheexpanderband,whilsttheotherendisrestrainedfrommovingbytheanchorblock（Fig.3.9（c））.

Whilstthisishappeningtheexpanderisalsopushedradiallyoutwards.Consequently,therewillbeatendencytoexpandthesynchronizingslitring,butthiswillbeopposedbythechamferedmouthoftheslidingsleeve.Thisenergizingactionattemptingtoexpandthesynchronizingringpreventstheslidingsleevefromcompletelymovingoverandengagingthedogteethoftheselectedgearwheeluntilboththedrivehubandconstantmeshgearwheelarerevolvingatthesamespeed.

Whenbothinputandoutputmembersareunified,thatis,rotatingasone,therecannotbeanymorefrictiontorquebecausethereisnorelativespeedtocreatethefrictionaldrag.Thereforetheexpanderbandimmediatelystopsexertingradialforceontheinsideofthesynchronizingring.

Theaxialthrustappliedbythegearsticktotheslidingsleevewillnowbesufficienttocompressthesplitsynchronizingringandsubsequentlypermitstheslee曹操曹操曹操非凡方法vetoslideoverthegearwheeldogteethforfullengagement（Fig.39（d））.

3.4Remotecontrolledgearselectionandengagementmechanisms

Gearselectionandengagementisachievedbytwodistinctmovements:

1Theselectionoftherequiredgearshiftgateandthepositioningoftheengagementgatelever.

2Theshiftingofthechosenselectorgaterodintotheengagementgearposition.

Thesetwooperationsaregenerallyperformedthroughthemediaoftheg