汽车专业英语第五章

CHAPTER5STEERINGANDSUSPENSIONSYSTEM5.1Basicpartsofsteeringsystem

Thebasicsteeringsysteminmostcarsisthesame.Thesteeringgearofsteeringboxistheheartofthesteeringsystem.Thisusuallyisnexttotheengine.Ashaftextendsfromthebackofthesteeringgear.Thisshaftisconnectedtothesteeringcolumnorsteeringshaft.Thesteeringwheelisatthetopofthesteeringcolumn.Anothershaftcomesfromthebottomofthesteeringgear.Thisshaftconnectstothearms,rods,andlinks.Thispartsassembly,calledthesteeringlinkage,connectsthesteeringgeartothepartsatthewheels.Thewheelsandtiresmounttothesteeringknuckles.AsshowninFig.5-1,theknucklesarepivotedatthetopandbottom.Thus,thewheelsandtirescanturnfromsidetoside.多数汽车的转向系基本上是一样的。转向系的核心是转向器，一般位于发动机附近。一根轴从转向器后部伸出，连接着转向柱。方向盘在转向柱的顶端。另一根轴从转向器低端伸出，连接着转向臂、转向拉杆和转向杆系，这些部件总称为转向传动机构，连接转向器和车轮上的部件。车轮和轮胎安装在转向节上。如图5-1所示，转向节的上下端可自由转动，这样车轮可从一侧转到另一侧。Whilethesteeringsystemmaylookcomplicated,itworksquitesimply.Whenadriverdrivesacarstraightdowntheroad,thesteeringgeariscentered.Thegearholdsthelinkagecenteredsothatthewheelsandtirespointstraightahead.Whenthedriverturnsthesteeringwheel,thesteeringshaftrotatesandthesteeringgearmovestowardthatside.Theshaftcomingoutthebottomofthesteeringgearturns,aswell.Whentheshaftturns,itpullsthelinkagetoonesideandmakesthesteeringknucklesturnslightlyabouttheirpivotpoints.Thus,thesteeringknuckle,spindle,wheels,andtiresturntooneside,causingthecartoturn.转向系看起来复杂，工作原理却很简单。汽车直行时，转向器处于中间位置，转向传动机构也处于中间位置，车轮直行。驾驶员转动方向盘，转向轴旋转，转向器向同侧转动，同时转向器底部的输出轴也会旋转。输出轴转动时，会向一侧拉动拉杆，使得转向节绕其支点旋转。这样，转向节、转向节轴端、车轮和轮胎都会向一侧旋转，汽车实现转向。Tominimizetirewearthefrontwheelsshouldbesteeredfromthestraightaheadtoapositionwheretheyformanangleof90ºtoalinedrawnfromtheinstantaneouscentertothewheelcenter.Itmeansthattheinnerwheelturnsthroughalargeranglethantheouterwheel.为减少轮胎的磨损，前轮应该从前进方向转到和瞬时转动中心到车轮中心的连线成90º角的位置，这表明内侧车轮比外侧车轮转过的角度要大。Itisobtainedbymakingthetrackrodadifferentlengthtothedistancebetweenthekingpins(orwheelswivelaxiscenters).Thetrackrodlengthissetsothatitsconnectiontothetrackarmfallsonanimaginarylinetakenfromthekingpintoapointonthevehiclecenterlinejustinfrontoftherearaxle.转向横拉杆的长度同主销间的距离不相等，就可保证各前轮以期望的角度旋转。转向横拉杆长度的设置要保证转向横拉杆与转向节臂的连接点位于主销到后桥前端汽车中心线上的点所形成的假想连线上。

ThemaintypesofSteeringBox.

recirculationballrackandpinionrecirculationballMostheavycommercialvehiclesusetherecirculationballtypeofsteeringgear.Thissteeringgearisdurable,withgoodsteeringresponseandgoodroadfeelforthedriver.多数重型商用车采用循环球式转向器，这类转向器性能稳定、转向灵敏而且路感好。Intherecirculationballsteeringgear,thewormshaftistheinputshaft.Thewormshaftconnectstothesteeringcolumninsuchawaythatamechaniccanremovethesteeringgearorsteeringcolumnindependentlyofoneanother.Thesectorshaft(alsocalledthepitmanshaft)isliketheoutputshaftofthesteeringgear.Themainpartsofthesteeringgeararetheballs,ballnut,andthegearteethontheballnut.在循环球式转向器中，转向螺杆是输入轴。这样转向螺杆连接着转向柱，修理工就可独立拆卸转向器或转向柱。齿扇轴（也叫摇臂轴）相当于转向器的输出轴．转向器的主要部件是钢球，转向螺母和转向螺母上的齿．Asthewormshaftturns,theballsmovetheballnutupanddownalongthewormshaft.Thisturnsthesectorshaft,sincethesectorteethmeshwiththeballnutteeth.Thesectorshaftisconnectedthroughsteeringlinkagetothefrontwheels.当转向螺杆转动时，刚球使球螺母沿转向螺杆上下运动．由于扇齿与球螺母齿啮合，齿扇轴转动．齿扇轴通过转向传动机构与前轮连接．rackandpinionTherack-and-pinionsystemhastwomainparts－thepinionandtherack.Thepinionisontheendofthesteeringcolumn.Thesteeringwheelturnsthepinion.Therackisalong,flatbarwithteethononeside.Therackteethmeshwiththeteethonthepinion.齿轮齿条转向器有两个主要部件－齿轮和齿条．齿轮安装在转向柱的末端．转向盘转动齿轮．齿条是一个一面有齿长平杆．齿条与齿轮啮合．Rack-and-pinionsteeringisusedonmanynewsmallercarsandonmostcarswithatransverseengine.Thissteeringgearissmallandlightweight.Itprovidesgoodsteeringwithminimumdrivereffort.Also,rack-and-pinionsteeringneedsfewerpartsinthesteeringgearandlinkage.Thus,itiseasytoservice.Rack-and-pinionsteeringgivesmorefeedbackandroadfeeltothedriver.很多新型小汽车和多数发动机横置的汽车都采用齿轮齿条式转向器。这类转向器尺寸小、重量轻，而且转向轻便。另外，转向器和转向传动机构所需的部件较少，便于维修。齿轮齿条式转向器为驾驶员提供了较好的反馈和路感．HydraulicPowerAssistedSteering(HPAS)液压助力转向系统Electro-HydraulicPowerSteering（EHPS）液压电动转向系统ElectricPowerAssistedSteering（EPAS或EPS）电动助力转向系统ActiveFrontSteering（AFS）主动前轮电动转向系统ElectricPowerSteeringbywire（EPS-bywire或SBW）线控电动转向系统5.4.3HydraulicPowerAssistedSteering

1.EnergySourceThepump－usuallyavane-typepumpwithinternalbypass－mustbedimensionedsuchthat,evenwiththeengineidling,itdeliversaflowofoilwithwhichitispossibletoachieveasteering-anglevelocityofatleast1.5s-1atthesteeringwheel.Athigherenginespeedsafurtherriseinthepressureoftheoilflowispreventedbyaflow-limitingvalveintegratedinthepump.这种泵通常是内部有旁通管路的叶片泵，标有型号，这样即使发动机空转时，它输送的油液能使转向盘达到至少1.5s-1转向角速度．发动机转速较高时，装在泵中的流量控制阀阻止了油压进一步增加．5.4.4ElectricPowerAssistedSteeringTheEPASsystemisreplacingthehydraulicsteeringsystemandisdestinedtosoonbecomemainstreamamongautomotivemanufacturers.Electricpowerassistedsteeringsystemsdonotrequireenginepowertooperate.Thus,avehicleequippedwithanEPASsystemmayachieveanestimatedthreepercentgreaterfueleconomythanthesamevehiclewithconventionalhydraulicpowersteering.电动转向助力系统正逐步代替液力转向系统并注定很快在汽车制造业中成为主流．电动转向助力系统不需要发动机动力驱动．这样，装备电动转向助力系统的汽车可以比装液力转向系统的同类型车辆节约大约３％的燃油．ActiveFrontSteering

主动前轮电动转向系统Atlow-speeddrivingincitytraffic,whenmuchsteeringworkisnecessary,theuseoftheelectricmotorprovidesfo