汽車專業(yè)英語第五章

CHAPTER5STEERINGANDSUSPENSIONSYSTEM5.1Basicpartsofsteeringsystem

Thebasicsteeringsysteminmostcarsisthesame.Thesteeringgearofsteeringboxistheheartofthesteeringsystem.Thisusuallyisnexttotheengine.Ashaftextendsfromthebackofthesteeringgear.Thisshaftisconnectedtothesteeringcolumnorsteeringshaft.Thesteeringwheelisatthetopofthesteeringcolumn.Anothershaftcomesfromthebottomofthesteeringgear.Thisshaftconnectstothearms,rods,andlinks.Thispartsassembly,calledthesteeringlinkage,connectsthesteeringgeartothepartsatthewheels.Thewheelsandtiresmounttothesteeringknuckles.AsshowninFig.5-1,theknucklesarepivotedatthetopandbottom.Thus,thewheelsandtirescanturnfromsidetoside.多數(shù)汽車的轉(zhuǎn)向系基本上是一樣的。轉(zhuǎn)向系的核心是轉(zhuǎn)向器，一般位于發(fā)動(dòng)機(jī)附近。一根軸從轉(zhuǎn)向器后部伸出，連接著轉(zhuǎn)向柱。方向盤在轉(zhuǎn)向柱的頂端。另一根軸從轉(zhuǎn)向器低端伸出，連接著轉(zhuǎn)向臂、轉(zhuǎn)向拉桿和轉(zhuǎn)向桿系，這些部件總稱為轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)，連接轉(zhuǎn)向器和車輪上的部件。車輪和輪胎安裝在轉(zhuǎn)向節(jié)上。如圖5-1所示，轉(zhuǎn)向節(jié)的上下端可自由轉(zhuǎn)動(dòng)，這樣車輪可從一側(cè)轉(zhuǎn)到另一側(cè)。Whilethesteeringsystemmaylookcomplicated,itworksquitesimply.Whenadriverdrivesacarstraightdowntheroad,thesteeringgeariscentered.Thegearholdsthelinkagecenteredsothatthewheelsandtirespointstraightahead.Whenthedriverturnsthesteeringwheel,thesteeringshaftrotatesandthesteeringgearmovestowardthatside.Theshaftcomingoutthebottomofthesteeringgearturns,aswell.Whentheshaftturns,itpullsthelinkagetoonesideandmakesthesteeringknucklesturnslightlyabouttheirpivotpoints.Thus,thesteeringknuckle,spindle,wheels,andtiresturntooneside,causingthecartoturn.轉(zhuǎn)向系看起來復(fù)雜，工作原理卻很簡單。汽車直行時(shí)，轉(zhuǎn)向器處于中間位置，轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)也處于中間位置，車輪直行。駕駛員轉(zhuǎn)動(dòng)方向盤，轉(zhuǎn)向軸旋轉(zhuǎn)，轉(zhuǎn)向器向同側(cè)轉(zhuǎn)動(dòng)，同時(shí)轉(zhuǎn)向器底部的輸出軸也會旋轉(zhuǎn)。輸出軸轉(zhuǎn)動(dòng)時(shí)，會向一側(cè)拉動(dòng)拉桿，使得轉(zhuǎn)向節(jié)繞其支點(diǎn)旋轉(zhuǎn)。這樣，轉(zhuǎn)向節(jié)、轉(zhuǎn)向節(jié)軸端、車輪和輪胎都會向一側(cè)旋轉(zhuǎn)，汽車實(shí)現(xiàn)轉(zhuǎn)向。Tominimizetirewearthefrontwheelsshouldbesteeredfromthestraightaheadtoapositionwheretheyformanangleof90otoalinedrawnfromtheinstantaneouscentertothewheelcenter.Itmeansthattheinnerwheelturnsthroughalargeranglethantheouterwheel.為減少輪胎的磨損，前輪應(yīng)該從前進(jìn)方向轉(zhuǎn)到和瞬時(shí)轉(zhuǎn)動(dòng)中心到車輪中心的連線成90o角的位置，這表明內(nèi)側(cè)車輪比外側(cè)車輪轉(zhuǎn)過的角度要大。Itisobtainedbymakingthetrackrodadifferentlengthtothedistancebetweenthekingpins(orwheelswivelaxiscenters).Thetrackrodlengthissetsothatitsconnectiontothetrackarmfallsonanimaginarylinetakenfromthekingpintoapointonthevehiclecenterlinejustinfrontoftherearaxle.轉(zhuǎn)向橫拉桿的長度同主銷間的距離不相等，就可保證各前輪以期望的角度旋轉(zhuǎn)。轉(zhuǎn)向橫拉桿長度的設(shè)置要保證轉(zhuǎn)向橫拉桿與轉(zhuǎn)向節(jié)臂的連接點(diǎn)位于主銷到后橋前端汽車中心線上的點(diǎn)所形成的假想連線上。

ThemaintypesofSteeringBox.

recirculationballrackandpinionrecirculationballMostheavycommercialvehiclesusetherecirculationballtypeofsteeringgear.Thissteeringgearisdurable,withgoodsteeringresponseandgoodroadfeelforthedriver.多數(shù)重型商用車采用循環(huán)球式轉(zhuǎn)向器，這類轉(zhuǎn)向器性能穩(wěn)定、轉(zhuǎn)向靈敏而且路感好。Intherecirculationballsteeringgear,thewormshaftistheinputshaft.Thewormshaftconnectstothesteeringcolumninsuchawaythatamechaniccanremovethesteeringgearorsteeringcolumnindependentlyofoneanother.Thesectorshaft(alsocalledthepitmanshaft)isliketheoutputshaftofthesteeringgear.Themainpartsofthesteeringgeararetheballs,ballnut,andthegearteethontheballnut.在循環(huán)球式轉(zhuǎn)向器中，轉(zhuǎn)向螺桿是輸入軸。這樣轉(zhuǎn)向螺桿連接著轉(zhuǎn)向柱，修理工就可獨(dú)立拆卸轉(zhuǎn)向器或轉(zhuǎn)向柱。齒扇軸（也叫搖臂軸）相當(dāng)于轉(zhuǎn)向器的輸出軸．轉(zhuǎn)向器的主要部件是鋼球，轉(zhuǎn)向螺母和轉(zhuǎn)向螺母上的齒．Asthewormshaftturns,theballsmovetheballnutupanddownalongthewormshaft.Thisturnsthesectorshaft,sincethesectorteethmeshwiththeballnutteeth.Thesectorshaftisconnectedthroughsteeringlinkagetothefrontwheels.當(dāng)轉(zhuǎn)向螺桿轉(zhuǎn)動(dòng)時(shí)，剛球使球螺母沿轉(zhuǎn)向螺桿上下運(yùn)動(dòng)．由于扇齒與球螺母齒嚙合，齒扇軸轉(zhuǎn)動(dòng)．齒扇軸通過轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)與前輪連接．rackandpinionTherack-and-pinionsystemhastwomainparts－thepinionandtherack.Thepinionisontheendofthesteeringcolumn.Thesteeringwheelturnsthepinion.Therackisalong,flatbarwithteethononeside.Therackteethmeshwiththeteethonthepinion.齒輪齒條轉(zhuǎn)向器有兩個(gè)主要部件－齒輪和齒條．齒輪安裝在轉(zhuǎn)向柱的末端．轉(zhuǎn)向盤轉(zhuǎn)動(dòng)齒輪．齒條是一個(gè)一面有齒長平桿．齒條與齒輪嚙合．Rack-and-pinionsteeringisusedonmanynewsmallercarsandonmostcarswithatransverseengine.Thissteeringgearissmallandlightweight.Itprovidesgoodsteeringwithminimumdrivereffort.Also,rack-and-pinionsteeringneedsfewerpartsinthesteeringgearandlinkage.Thus,itiseasytoservice.Rack-and-pinionsteeringgivesmorefeedbackandroadfeeltothedriver.很多新型小汽車和多數(shù)發(fā)動(dòng)機(jī)橫置的汽車都采用齒輪齒條式轉(zhuǎn)向器。這類轉(zhuǎn)向器尺寸小、重量輕，而且轉(zhuǎn)向輕便。另外，轉(zhuǎn)向器和轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)所需的部件較少，便于維修。齒輪齒條式轉(zhuǎn)向器為駕駛員提供了較好的反饋和路感．HydraulicPowerAssistedSteering(HPAS)液壓助力轉(zhuǎn)向系統(tǒng)Electro-HydraulicPowerSteering（EHPS）液壓電動(dòng)轉(zhuǎn)向系統(tǒng)ElectricPowerAssistedSteering（EPAS或EPS）電動(dòng)助力轉(zhuǎn)向系統(tǒng)ActiveFrontSteering（AFS）主動(dòng)前輪電動(dòng)轉(zhuǎn)向系統(tǒng)ElectricPowerSteeringbywire（EPS-bywire或SBW）線控電動(dòng)轉(zhuǎn)向系統(tǒng)5.4.3HydraulicPowerAssistedSteering

1.EnergySourceThepump－usuallyavane-typepumpwithinternalbypass－mustbedimensionedsuchthat,evenwiththeengineidling,itdeliversaflowofoilwithwhichitispossibletoachieveasteering-anglevelocityofatleast1.5s-1atthesteeringwheel.Athigherenginespeedsafurtherriseinthepressureoftheoilflowispreventedbyaflow-limitingvalveintegratedinthepump.這種泵通常是內(nèi)部有旁通管路的葉片泵，標(biāo)有型號，這樣即使發(fā)動(dòng)機(jī)空轉(zhuǎn)時(shí)，它輸送的油液能使轉(zhuǎn)向盤達(dá)到至少1.5s-1轉(zhuǎn)向角速度．發(fā)動(dòng)機(jī)轉(zhuǎn)速較高時(shí)，裝在泵中的流量控制閥阻止了油壓進(jìn)一步增加．5.4.4ElectricPowerAssistedSteeringTheEPASsystemisreplacingthehydraulicsteeringsystemandisdestinedtosoonbecomemainstreamamongautomotivemanufacturers.Electricpowerassistedsteeringsystemsdonotrequireenginepowertooperate.Thus,avehicleequippedwithanEPASsystemmayachieveanestimatedthreepercentgreaterfueleconomythanthesamevehiclewithconventionalhydraulicpowersteering.電動(dòng)轉(zhuǎn)向助力系統(tǒng)正逐步代替液力轉(zhuǎn)向系統(tǒng)并注定很快在汽車制造業(yè)中成為主流．電動(dòng)轉(zhuǎn)向助力系統(tǒng)不需要發(fā)動(dòng)機(jī)動(dòng)力驅(qū)動(dòng)．這樣，裝備電動(dòng)轉(zhuǎn)向助力系統(tǒng)的汽車可以比裝液力轉(zhuǎn)向系統(tǒng)的同類型車輛節(jié)約大約３％的燃油．ActiveFrontSteering

主動(dòng)前輪電動(dòng)轉(zhuǎn)向系統(tǒng)Atlow-speeddrivingincitytraffic,whenmuchsteeringworkisnecessary,theuseoftheelectricmotorprovidesfo