- 1 -Steering GearAlong with automobile electronic technology swift and violent development,the people also day enhance to the motor turning handling quality request.The motor turning system changed,the hydraulic pressure boost from the traditional machinery changes(Hydraulic Power Steering,is called HPS),the electrically controlled hydraulic pressure boost changes(Electric Hydraulic Power Steering,is called EHPS),develops the electrically operated boost steering system( Electric Power Steering,is called ESP),finally also will transit to the line controls the steering system(Steer By Wire,will be called SBW).The machinery steering system is refers by pilot's physical strength achievement changes the energy,in which all power transmission all is mechanical,the automobile changes the movement is operates the steering wheel by the pilot,transmits through the diverter and a series of members changes the wheel to realize.The mechanical steering system by changes the control mechanism,the diverter and major part gearing changes 3 to be composed.Usually may divide into according to the mechanical diverter form:The gear rack type,follows round the work-like,the worm bearing adjuster hoop type,the worm bearing adjuster refers sells the type,Is the gear rack type and follows using the broadest two kinds round the word-like(uses in needing time big steering force).In follows round the word-like in the diverter,the input changes the circle and the output steering arm pivot angle is proportional;In the gear rack type diverter,the input changes the turn and the output rack displacement is proportional.Follows round the world-like the diverter because is the rolling friction from,thus the transmission efficiency is very high,the ease of operation also the service life are long,moreover bearing capacity ,therefore widely applies on the truck.The gear rack type diverter with follows round the work-like compares,the most major characteristic is the rigidity is big,the structure compact weight is light,also the cost is low.Because this way passes on easily by the wheel the reacting force the steering wheel,therefore has to the pavement behavior response keen merit,but simultaneously also easy to have - 2 -phenomena and so on go on and oscillation,also its load bearing efficiency relative weak,therefore mainly applies on the compact car and the pickup truck,at present the majority of low end passenger vehicle uses is the gear rack type machinery steering system.Along with the vehicles carrying capacity increase as well as the people to the vehicles handling quality request enhancement,the simple mechanical type steering system were already unable to meet the needs,the power steering system arise at the historic moment,it could rotate the steering wheel while the pilot to provide the boost,the power steering system divides into the hydraulic pressure steering system and the electrically operated steering system 2kinds.Hydraulic pressure steering system is at present uses the most widespread steering system.The hydraulic pressure steering system increased the hydraulic system in the mechanical system foundation,including hydraulic pump,V shape band pulley,drill tubing,feed installment,boost installment and control valve.It with the aid of in the motor car engine power actuation hydraulic pump,the air compressor and the generator and so on,by the fluid strength,the physical strength or the electric power increases the pilot to operate the strength which the front wheel changes,enables the pilot to be possible nimbly to operate motor turning facilely,reduced the labor intensity,enhanced the travel security.The hydraulic pressure boost steering system from invented already had about half century history to the present,might say was one kind of more perfect system， because its work reliable,the technology mature still widely is applied until now.It takes the power supply by the hydraulic pump,after oil pipe-line control valves to power hydraulic cylinder feed,through the connecting rod impetus rotation gear movement,may changes the boost through the change cylinder bore and the flowing tubing head pressure size the size,from this achieved changes the boost the function. The traditional hydraulic pressure type power steering system may divide into generally according to the liquid flow form: Ordinary flow type and atmospheric pressure type 2 kind of types,also may divide into according to the control valve form transfers the valve type and the slide-valve type.- 3 -Along with hydraulic pressure power steering system on automobile daily popularization,the people to operates when the portability and the road feeling request also day by day enhance,however the hydraulic pressure power steering system has many shortcomings actually: ①Because its itself structure had decided it is unable to guarantee vehicles rotates the steering wheel when any operating mode,all has the ideal operation stability,namely is unable simultaneously to guarantee time the low speed changes the portability and the high speed time operation stability;② The automobile changes the characteristic to drive the pilot technical the influence to be serious;③The steering ratio is fixed,causes the motor turning response characteristic along with changes and so on vehicle speed,transverse acceleration to change,the pilot must aim at the motor turning characteristic peak-to-peak value and the phase change ahead of time carries on certain operation compensation,thus controls the automobile according to its wish travel.Like this increased pilot's operation burden,also causes in the motor turning travel not to have the security hidden danger;But hereafter appeared the electrically controlled hydraulic booster system,it increases the velocity generator in the traditional hydraulic pressure power steering system foundation,enables the automobile along with the vehicle speed change automatic control force size,has to a certain extent relaxed the traditional hydraulic pressure steering system existence question.At present our country produces on the commercial vehicle and the passenger vehicle uses mostly is the electrically controlled hydraulic pressure boost steering system,it is quite mature and the application widespread steering system.Although the electrically controlled hydraulic servo alleviated the traditional hydraulic pressure from certain degree to change between the portability and the road feeling contradiction,however it did not have fundamentally to solve the HPS system existence insufficiency,along with automobile microelectronic technology development,automobile fuel oil energy conservation request as well as global initiative environmental protection,it in aspect and so on arrangement,installment, leak-proof quality,control sensitivity,energy consumption,attrition and noise insufficiencies already more and more obvious,the steering system turned towards the - 4 -electrically operated boost steering system development.The electrically operated boost steering system is the present motor turning system development direction,its principle of work is:EPS system ECU after comes from the steering wheel torque sensor and the vehicle speed sensor signal carries on analysis processing,controls the electrical machinery to have the suitable boost torque,assists the pilot to complete changes the operation.In the last few years,along with the electronic technology development,reduces EPS the cost to become large scale possibly,Japan sends the car company,Mitsubishi Car company,this field car company,US's Delphi automobile system company,TRW Corporation and Germany's ZF Corporation greatly all one after another develops EPS.Mercedes2Benz and Siemens Automotive Two big companies invested 65,000,000 pounds to use in developing EPS,the goal are together load a car to 2002,yearly produce 300 ten thousand sets,became the global EPS manufacturer.So far,the EPS system in the slight passenger vehicle,on the theater box type vehicle obtains the widespread application, and every year by 300 ten thousand speed development.Steering is the term applied to the collection of components,linkages,etc.which allow for a vessel (ship,boat) or vehicle (car) to follow the desired course.An exception is the case of rail transport by which rail tracks combined together with railroad switches provide the steering function.The most conventional steering arrangement is to turn the front wheels using a hand–operated steering wheel which is positioned in front of the driver,via the steering column,which may contain universal joints to allow it to deviate somewhat from a straight line.Other arrangements are sometimes found on different types of vehicles,for example,a tiller or rear-wheel steering.Tracked vehicles such as tanks usually employ differential steering -that is,the tracks are made to move at different speeds or even in opposite directions to bring about a change of course.Many modern cars use rack and pinion steering mechanisms,where the steering wheel turns the pinion gear;the pinion moves the rack,which is a sort of linear gear which meshes with the pinion,from side to side.This motion applies steering torque to the kingpins of the steered wheels via tie rods and a short lever arm called the steering - 5 -arm.Older designs often use the recirculating ball mechanism,which is still found on trucks and utility vehicles.This is a variation on the older worm and sector design; the steering column turns a large screw (the "worm gear") which meshes with a sector of a gear,causing it to rotate about its axis as the worm gear is turned;an arm attached to the axis of the sector moves the pitman arm,which is connected to the steering linkage and thus steers the wheels.The recirculating ball version of this apparatus reduces the considerable friction by placing large ball bearings between the teeth of the worm and those of the screw;at either end of the apparatus the balls exit from between the two pieces into a channel internal to the box which connects them with the other end of the apparatus,thus they are "recirculated".The rack and pinion design has the advantages of a large degree of feedback and direct steering "feel";it also does not normally have any backlash,or slack.A disadvantage is that it is not adjustable,so that when it does wear and develop lash,the only cure is replacement.The recirculating ball mechanism has the advantage of a much greater mechanical advantage,so that it was found on larger,heavier vehicles while the rack and pinion was originally limited to smaller and lighter ones;due to the almost universal adoption of power steering,however,this is no longer an important advantage,leading to the increasing use of rack and pinion on newer cars.The recirculating ball design also has a perceptible lash,or "dead spot" on center,where a minute turn of the steering wheel in either direction does not move the steering apparatus;this is easily adjustable via a screw on the end of the steering box to account for wear,but it cannot be entirely eliminated or the mechanism begins to wear very rapidly.This design is still in use in trucks and other large vehicles,where rapidity of steering and direct feel are less important than robustness,maintainability,and mechanical advantage.The much smaller degree of feedback with this design can also sometimes be an advantage;drivers of vehicles with rack and pinion steering can have their thumbs broken when a front wheel hits a bump,causing the steering wheel to kick to one side suddenly (leading to driving instructors telling students to keep their - 6 -thumbs on the front of the steering wheel,rather than wrapping around the inside of the rim).This effect is even stronger with a heavy vehicle like a truck;recirculating ball steering prevents this degree of feedback,just as it prevents desirable feedback under normal circumstances.The steering linkage connecting the steering box and the wheels usually conforms to a variation of Ackermann steering geometry,to account for the fact that in a turn,the inner wheel is actually traveling a path of smaller radius than the outer wheel,so that the degree of toe suitable for driving in a straight path is not suitable for turns.As vehicles have become heavier and switched to front wheel drive,the effort to turn the steering wheel manually has increased often to the point where major physical exertion is required.To alleviate this,auto makers have developed power steering systems.there are two types of power steering systems-hydraulic and electric electronic.there is also a hydraulic-electric hybrid system possible.A hydraulic power steering(HPS)uses hydraulic pressure supplied by an engine-driven pump to assist the motion of turning the steering wheel.Electric power steering(ESP)is more efficient than the hydraulic power steering,since the electric power steering motor only needs to provide assist when the steering wheel is turned,whereas the hydraulic pump must run constantly.In ESP the assist level is easily tunable to the vehicle type,road speed,and even driver preference.An added benefit is the elimination of environmental hazard posed by leakage and disposal of hydraulic power steering fluid.An outgrowth of power steering is speed adjustable steering,where the steering is heavily assisted at low speed and lightly assisted at high speed.The auto makers perceive that motorists might need to make large steering inputs while manoeuvering for parking,but not while traveling at high speed.The first vehicle with this feature was the Citroen SM with its Diravi layout,although rather than altering the amount of assistance as in modern power steering systems,it altered the pressure on a centring cam which made the the steering wheel try to “spring”back to the straight-ahead position.Modern speed-adjustable power steering systems reduce the pressure fed to - 7 -the ram as the speed increases,giving a more direct feel.This feature is gradually becoming commonplace across all new vehicles.Four-wheel steering(or all wheel steering)is a system employed by some vehicles to increase vehicle stability while maneuvering at high speed,or to decrease turning radius at low speed.In most four-wheel steering systems,the rear wheel are steered by a computer and actuators.The rear wheel generally cannot turn as far as the Alternatively,several systems,including Delphi's Quadrasteer and the system in Honda's Prelude line,allow for the rear wheels to be steered in the opposite direction as the front wheels during low speeds.This allows the vehicle to turn in a significantly smaller radius-sometimes critical for large trucks or vehicles with trailers. - 8 -汽車轉(zhuǎn)向器隨著汽車電子技術(shù)的迅猛發(fā)展，人們對(duì)汽車轉(zhuǎn)向操縱性能的要求也日益提 高。汽車轉(zhuǎn)向系統(tǒng)已從傳統(tǒng)機(jī)械轉(zhuǎn)向、液壓助力轉(zhuǎn)向(Hydraulic Power Steering ，簡(jiǎn)稱 HPS)、電控液壓助力轉(zhuǎn)向( Electric Hydraulic Power Steering ，簡(jiǎn)稱 EHPS)，發(fā)展到電動(dòng)助力轉(zhuǎn)向系統(tǒng)(Electric Power Steering，簡(jiǎn)稱 EPS)，最終還將過(guò)渡到線控轉(zhuǎn)向系統(tǒng)(Steer By Wire，簡(jiǎn)稱SBW)。機(jī)械轉(zhuǎn)向系統(tǒng)是指以駕駛員的體力作為轉(zhuǎn)向能源，其中所有傳力件都是機(jī)械 的，汽車的轉(zhuǎn)向運(yùn)動(dòng)是由駕駛員操縱方向盤，通過(guò)轉(zhuǎn)向器和一系列的桿件傳遞到 轉(zhuǎn)向車輪而實(shí)現(xiàn)的。機(jī)械轉(zhuǎn)向系由轉(zhuǎn)向操縱機(jī)構(gòu)、轉(zhuǎn)向器和轉(zhuǎn)向傳動(dòng)機(jī)械3大部 分組成。通常根據(jù)機(jī)械式轉(zhuǎn)向器形式可以分為:齒輪齒條式、循環(huán)球式、蝸桿滾輪式、蝸桿指銷式。應(yīng)用最廣的兩種是齒輪齒條式和循環(huán)球式(用于需要較大的轉(zhuǎn)向力 時(shí))。在循環(huán)球式轉(zhuǎn)向器中，輸入轉(zhuǎn)向圈與輸出的轉(zhuǎn)向搖臂擺角是成正比的；在齒輪齒條式轉(zhuǎn)向器中，輸入轉(zhuǎn)向圈數(shù)與輸出的齒條位移是成正比的。循環(huán)球式轉(zhuǎn)向器由于是滾動(dòng)摩擦形式，因而正傳動(dòng)效率很高，操作方便且使用壽命長(zhǎng)，而且承載能力強(qiáng)，故廣泛應(yīng)用于載貨汽車上。齒輪齒條式轉(zhuǎn)向器與循環(huán)球式相比，最大特點(diǎn)是剛性大，結(jié)構(gòu)緊湊重量輕，且成本低。由于這種方式容易由車輪將反作用力傳至轉(zhuǎn)向盤，所以具有對(duì)路面狀態(tài)反應(yīng)靈敏的優(yōu)點(diǎn)，但同時(shí)也容易產(chǎn)生打手和擺振等現(xiàn)象，且其承載效率相對(duì)較弱，故主要應(yīng)用于小汽車及輕型貨車上，目前大部分低端轎車采用的就是齒輪齒條式機(jī)械轉(zhuǎn)向系統(tǒng)。隨著車輛載重的增加以及人們對(duì)車輛操縱性能要求的提高，簡(jiǎn)單的機(jī)械式轉(zhuǎn)向系統(tǒng)已經(jīng)無(wú)法滿足需要，動(dòng)力轉(zhuǎn)向系統(tǒng)應(yīng)運(yùn)而生，它能在駕駛員轉(zhuǎn)動(dòng)方向盤的同時(shí)提供助力，動(dòng)力轉(zhuǎn)向系統(tǒng)分為液壓轉(zhuǎn)向系統(tǒng)和電動(dòng)轉(zhuǎn)向系統(tǒng) 2種。其中液壓轉(zhuǎn)向系統(tǒng)是目前使用最為廣泛的轉(zhuǎn)向系統(tǒng)。液壓轉(zhuǎn)向系統(tǒng)在機(jī)械系統(tǒng)的基礎(chǔ)上增加了液壓系統(tǒng)，包括液壓泵、V 形帶輪、油管、供油裝置、助力裝置和控制閥。它借助于汽車發(fā)動(dòng)機(jī)的動(dòng)力驅(qū)動(dòng)液壓泵、空氣壓縮機(jī)和發(fā)電機(jī)等，以液力、氣力或電力增大駕駛員操縱前輪轉(zhuǎn)向的力量，使駕駛員可以輕便靈活地操縱汽車轉(zhuǎn)向，減輕了勞動(dòng)強(qiáng)度，提高了行- 9 -駛安全性。液壓助力轉(zhuǎn)向系統(tǒng)從發(fā)明到現(xiàn)在已經(jīng)有了大約半個(gè)世紀(jì)的歷史，可以說(shuō)是一種較為完善的系統(tǒng)，由于其工作可靠、技術(shù)成熟至今仍被廣泛應(yīng)用。它由液壓泵作為動(dòng)力源，經(jīng)油管道控制閥向動(dòng)力液壓缸供油，通過(guò)活塞桿帶動(dòng)轉(zhuǎn)向機(jī)構(gòu)動(dòng)作，可通過(guò)改變缸徑及油壓的大小來(lái)改變助力的大小，由此達(dá)到轉(zhuǎn)向助力的作用。傳統(tǒng)液壓式動(dòng)力轉(zhuǎn)向系統(tǒng)一般按液流的形式可以分為:常流式和常壓式2種類型，也可根據(jù)控制閥形式分為轉(zhuǎn)閥式和滑閥式。隨著液壓動(dòng)力轉(zhuǎn)向系統(tǒng)在汽車上的日益普及，人們對(duì)操作時(shí)的輕便性和路感的要求也日益提高，然而液壓動(dòng)力轉(zhuǎn)向系統(tǒng)卻存在許多的缺點(diǎn)：①由于其本身的結(jié)構(gòu)決定了其無(wú)法保證車輛在任何工況下轉(zhuǎn)動(dòng)轉(zhuǎn)向盤時(shí)，都有較理想的操縱穩(wěn)定性，即無(wú)法同時(shí)保證低速時(shí)的轉(zhuǎn)向輕便性和高速時(shí)的操縱穩(wěn)定性；②汽車的轉(zhuǎn)向特性受駕駛員駕駛技術(shù)的影響嚴(yán)重；③轉(zhuǎn)向傳動(dòng)比固定，使汽車轉(zhuǎn)向響應(yīng)特性隨車速、側(cè)向加速度等變化而變化，駕駛員必須提前針對(duì)汽車轉(zhuǎn)向特性幅值和相位 的變化進(jìn)行一定的操作補(bǔ)償，從而控制汽車按其意愿行駛。這樣增加了駕駛員的 操縱負(fù)擔(dān)，也使汽車轉(zhuǎn)向行駛中存在不安全隱患；而此后出現(xiàn)了電控液壓助力系統(tǒng)，它在傳統(tǒng)的液壓動(dòng)力轉(zhuǎn)向系統(tǒng)的基礎(chǔ)上增加速度傳感器，使汽車能夠隨著車速的變化自動(dòng)調(diào)節(jié)操縱力的大小，在一定程度上緩和了傳統(tǒng)的液壓轉(zhuǎn)向系統(tǒng)存在 的問(wèn)題。目前我國(guó)生產(chǎn)的商用車和轎車上采用的大多是電控液壓助力轉(zhuǎn)向系統(tǒng)，它是比較成熟和應(yīng)用廣泛的轉(zhuǎn)向系統(tǒng)。盡管電控液壓助力裝置從一定程度上緩解了傳統(tǒng)的液壓轉(zhuǎn)向中輕便性和路感之間的矛盾，然而它還是沒(méi)有從根本上解決HPS系統(tǒng)存在的不足，隨著汽車微電子技術(shù)的發(fā)展，汽車燃油節(jié)能的要求以及全球性倡導(dǎo)環(huán)保，其在布置、安裝、密封性、操縱靈敏度、能量消耗、磨損與噪聲等方面的不足已越來(lái)越明顯，轉(zhuǎn)向系統(tǒng)向著電動(dòng)助力轉(zhuǎn)向系統(tǒng)發(fā)展。電動(dòng)助力轉(zhuǎn)向系統(tǒng)是現(xiàn)在汽車轉(zhuǎn)向系統(tǒng)的發(fā)展方向，其工作原理是:EPS 系統(tǒng)的 ECU對(duì)來(lái)自轉(zhuǎn)向盤轉(zhuǎn)矩傳感器和車速傳感器的信號(hào)進(jìn)行分析處理后，控制電機(jī)產(chǎn)生適當(dāng)?shù)闹D(zhuǎn)矩，協(xié)助駕駛員完成轉(zhuǎn)向操作。近幾年來(lái)，隨著電子技術(shù)的發(fā)展，大幅度降低 EPS的成本已成為可能，日本的大發(fā)汽車公司、三菱汽車公司、 本田汽車公司、美國(guó)的 Delphi汽車系統(tǒng)公司、TRW 公司及德國(guó)的 ZF- 10 -公司都相繼研制出 EPS。Mercedes2Benz 和 Siemens Automotive 兩大公司共同投資 6500萬(wàn)英鎊用于開(kāi)發(fā) EPS ，目標(biāo)是到 2002年裝車，年產(chǎn) 300萬(wàn)套，成為全球 EPS制造商。到目前為止，EPS 系統(tǒng)在輕微型轎車、廂式車上得到廣泛的應(yīng)用，并且每年以 300萬(wàn)臺(tái)的速度發(fā)展。轉(zhuǎn)向是一個(gè)專業(yè)術(shù)語(yǔ)，適用于采集部件，聯(lián)系等，其中允許一艘(艦船)或汽車(轎車)按照預(yù)期的方向行駛。一個(gè)例外的情況是鐵路運(yùn)輸由路軌組合在一起鐵路 道岔提供轉(zhuǎn)向功能。許多現(xiàn)代轎車使用齒輪齒條式轉(zhuǎn)向器，在方向盤末端有轉(zhuǎn)動(dòng)齒輪；該齒輪帶動(dòng)齒條移動(dòng)，它是一種線性的齒輪緊密配合，從一邊到一邊。這種運(yùn)動(dòng)把轉(zhuǎn)矩通過(guò)轉(zhuǎn)向橫拉桿和一種叫做轉(zhuǎn)向節(jié)臂的短形臂傳遞給轉(zhuǎn)向輪的主銷。以前的設(shè)計(jì)往往采用循環(huán)球式轉(zhuǎn)向器，而這種轉(zhuǎn)向器仍然應(yīng)用在卡車和多用途車輛。這是一種老式的螺母和齒扇設(shè)計(jì)，該轉(zhuǎn)向管柱轉(zhuǎn)動(dòng)大螺絲("蝸輪")，它與一個(gè)齒扇齒輪嚙合，當(dāng)蝸輪轉(zhuǎn)動(dòng)時(shí)，齒扇也隨之轉(zhuǎn)動(dòng)，一個(gè)安裝在齒扇軸上且與轉(zhuǎn)向聯(lián)動(dòng)有關(guān)的搖臂帶動(dòng)轉(zhuǎn)向節(jié)臂，從而使車輪轉(zhuǎn)動(dòng)循環(huán)球式轉(zhuǎn)向器通過(guò)安裝滾珠減少螺母和螺桿之間的摩擦；兩根導(dǎo)管和螺母內(nèi)的螺旋管狀通道組合成兩條各自獨(dú)立的封閉的鋼球“流到” 。齒輪齒條式轉(zhuǎn)向器設(shè)計(jì)具有很大程度的反饋和直接轉(zhuǎn)向"路感"；它也通常不會(huì)有任何反彈，或呆滯。缺點(diǎn)是，它是不可調(diào)的，因此當(dāng)它磨損唯一的解決辦法更換。循環(huán)球式轉(zhuǎn)向器的優(yōu)點(diǎn)是機(jī)械優(yōu)勢(shì)，因此，它被使用在較大較重的車輛，而齒輪齒條式原本僅限于較小和較輕；由于幾乎普遍采用動(dòng)力轉(zhuǎn)向系統(tǒng)，不過(guò)，這已不再是一個(gè)重要的優(yōu)勢(shì)，導(dǎo)致越來(lái)越多地在新型汽車應(yīng)用齒輪齒條式轉(zhuǎn)向器。循環(huán)球式轉(zhuǎn)向器設(shè)計(jì)在中心也有明顯的沖擊，或"死點(diǎn)"。凡一分鐘交替方向盤出不來(lái)并不移動(dòng)轉(zhuǎn)向機(jī)構(gòu)；這是很容易可調(diào)螺桿的端部來(lái)減少磨損，但它并不能完全消除或機(jī)制開(kāi)始磨損很快。這項(xiàng)設(shè)計(jì)目前仍在使用中，在卡車和其他大型車輛，也應(yīng)用于迅速轉(zhuǎn)向，路感與穩(wěn)健性，可維護(hù)性，和機(jī)械的優(yōu)勢(shì)相比不太重要的場(chǎng)合。較小程度的反饋，這樣的設(shè)計(jì)也有時(shí)是一種優(yōu)點(diǎn)；當(dāng)前輪碰撞時(shí)，使用齒輪齒條轉(zhuǎn)向的司機(jī)只有自己的大拇指受傷，造成方向盤揭開(kāi)一邊突然(因?yàn)轳{駛教練告訴學(xué)生把自己的大拇指在前面的方向盤，而非放在左右- 11 -的內(nèi)邊緣)。這種效果在像卡車一樣的重型汽車更為明顯；循環(huán)球式轉(zhuǎn)向防止這種程度的反饋，只是因?yàn)樗梢栽谡Ｇ闆r下防止可取反饋。轉(zhuǎn)向連鎖連接轉(zhuǎn)向器和車輪通常符合一個(gè)阿克曼轉(zhuǎn)向幾何的變化，它交代了一個(gè)事實(shí):當(dāng)轉(zhuǎn)向時(shí)，內(nèi)輪轉(zhuǎn)過(guò)的半徑比外輪小得多，因此適合駕駛的直路，是不適合曲折。由于車輛已成為較重而改用前輪驅(qū)動(dòng)，為了扭轉(zhuǎn)方向盤，通常的，主要的是體 力。為了解決這一問(wèn)題，汽車業(yè)發(fā)展的動(dòng)力轉(zhuǎn)向系統(tǒng)。有兩種類型的助力轉(zhuǎn)向系 統(tǒng)-液壓和電氣/電子。還有一種液壓-電動(dòng)混合系統(tǒng)。 液壓助力轉(zhuǎn)向系統(tǒng)(HPS)利用油壓供應(yīng)的一個(gè)發(fā)動(dòng)機(jī)驅(qū)動(dòng)泵，以協(xié)助將方向盤轉(zhuǎn)轉(zhuǎn)動(dòng)。電動(dòng)助力轉(zhuǎn)向系統(tǒng)(EPS)方式，是較有效率的液壓助力轉(zhuǎn)向系統(tǒng)，由于電 動(dòng)助力轉(zhuǎn)向汽車只需要提供協(xié)助時(shí)，方向盤被轉(zhuǎn)動(dòng)，而液壓泵必須不斷運(yùn)行。 在 EPS 的幫助下是很容易調(diào)節(jié)車型，最高車速，甚至駕駛的喜好。 另外一個(gè)好處是， 通過(guò)泄漏和處置動(dòng)力轉(zhuǎn)向液消除對(duì)環(huán)境構(gòu)成危險(xiǎn)。動(dòng)力轉(zhuǎn)向的分支是速度可調(diào)轉(zhuǎn)向而轉(zhuǎn)向是大量輔助以低速行駛，稍微協(xié)助高 速。 汽車制造商認(rèn)為，當(dāng)要停車時(shí)駕駛?cè)丝赡苄枰龀龃罅哭D(zhuǎn)向投入，但當(dāng)時(shí)高 速行駛時(shí)則不然。第一輛有這特點(diǎn)的汽車，是雪鐵龍與其 diravi，雖然改變了現(xiàn)代汽車轉(zhuǎn)向系統(tǒng)資金的投入，但它改變了定心凸輪的壓力，使得方向盤盡力去回到原來(lái)的位置?，F(xiàn)代速度可調(diào)式動(dòng)力轉(zhuǎn)向系統(tǒng)，當(dāng)速度增長(zhǎng)時(shí)減少了活塞的壓力,給予更直接的感受.這一特點(diǎn)在所有新車正逐漸成為司空見(jiàn)慣。四輪轉(zhuǎn)向(或全輪轉(zhuǎn)向)是一種系統(tǒng)，當(dāng)高速行駛時(shí)能增加車輛穩(wěn)定型，而在低 速行駛時(shí)可以減小轉(zhuǎn)彎半徑。 大多數(shù)的四輪轉(zhuǎn)向系統(tǒng)，后輪轉(zhuǎn)向通過(guò)單片機(jī)和驅(qū)動(dòng)器實(shí)現(xiàn)。 后輪一般不能 反過(guò)來(lái)，有幾個(gè)系統(tǒng)，包括 Delphi的 quadrasteer，該系統(tǒng)在本田的生產(chǎn)前線，當(dāng)前輪低速時(shí)，允許后輪在相反方向轉(zhuǎn)向。這使得車輛轉(zhuǎn)彎半徑較小，有時(shí)應(yīng)用于大 型卡車車輛及掛車。