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譯文題目： Automotive brake systems
汽車制動(dòng)系統(tǒng)
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要求學(xué)生結(jié)合畢業(yè)設(shè)計(jì)（論文）課題參閱一篇以上的外文資料，并翻譯至少一萬(wàn)印刷符（或譯出3千漢字）以上的譯文。譯文原則上要求打?。ㄈ缡謱懀宦捎?00字方格稿紙書寫），連同學(xué)校提供的統(tǒng)一封面及英文原文裝訂，于畢業(yè)設(shè)計(jì)（論文）工作開始后2周內(nèi)完成，作為成績(jī)考核的一部分。
Automobile?Brake?System?
The?braking?system?is?the?most?important?system?in?cars.?If?the?brakes?fail,?the?result?can?be?disastrous.?Brakes?are?actually?energy?conversion?devices,?which?convert?the?kinetic?energy?(momentum)?of?the?vehicle?into?thermal?energy?(heat).When?stepping?on?the?brakes,?the?driver?commands?a?stopping?force?ten?times?as?powerful?as?the?force?that?puts?the?car?in?motion.?The?braking?system?can?exert?thousands?of?pounds?of?pressure?on?each?of?the?four?brakes.?
Two?complete?independent?braking?systems?are?used?on?the?car.?They?are?the?service?brake?and?the?parking?brake.?
The?service?brake?acts?to?slow,?stop,?or?hold?the?vehicle?during?normal?driving.?They?are?foot-operated?by?the?driver?depressing?and?releasing?the?brake?pedal.?The?primary?purpose?of?the?parking?brake?is?to?hold?the?vehicle?stationary?while?it?is?unattended.?The?parking?brake?is?mechanically?operated?by?when?a?separate?parking?brake?foot?pedal?or?hand?lever?is?set.?
??The?brake?system?is?composed?of?the?following?basic?components:?the?“master?cylinder”?which?is?located?under?the?hood,?and?is?directly?connected?to?the?brake?pedal,?converts?driver?foot’s?mechanical?pressure?into?hydraulic?pressure.?Steel?“brake?lines”?and?flexible?“brake?hoses”?connect?the?master?cylinder?to?the?“slave?cylinders”?located?at?each?wheel.?Brake?fluid,?specially?designed?to?work?in?extreme?conditions,?fills?the?system.?“Shoes”?and?“pads”?are?pushed?by?the?slave?cylinders?to?contact?the?“drums”?and?“rotors”?thus?causing?drag,?which?(hopefully)?slows?the?car.
The?typical?brake?system?consists?of?disk?brakes?in?front?and?either?disk?or?drum?brakes?in?the?rear?connected?by?a?system?of?tubes?and?hoses?that?link?the?brake?at?each?wheel?to?the?master?cylinder?(Figure).?
Basically,?all?car?brakes?are?friction?brakes.?When?the?driver?applies?the?brake,?the?control?device?forces?brake?shoes,?or?pads,?against?the?rotating?brake?drum?or?disks?at?wheel.?Friction?between?the?shoes?or?pads?and?the?drums?or?disks?then?slows?or?stops?the?wheel?so?that?the?car?is?braked.?
In?most?modern?brake?systems?(see?Figure?15.1),?there?is?a?fluid-filled?cylinder,?called?master?cylinder,?which?contains?two?separate?sections,?there?is?a?piston?in?each?section?and?both?pistons?are?connected?to?a?brake?pedal?in?the?driver’s?compartment.?When?the?brake?is?pushed?down,?brake?fluid?is?sent?from?the?master?cylinder?to?the?wheels.?
At?the?wheels,?the?fluid?pushes?shoes,?or?pads,?against?revolving?drums?or?disks.?The?friction?between?the?stationary?shoes,?or?pads,?and?the?revolving?drums?or?disks?slows?and?stops?them.?This?slows?or?stops?the?revolving?wheels,?which,?in?turn,?slow?or?stop?the?car.??The?brake?fluid?reservoir?is?on?top?of?the?master?cylinder.?Most?cars?today?have?a?transparent?reservoir?so?that?you?can?see?the?level?without?opening?the?cover.?The?brake?fluid?level?will?drop?slightly?as?the?brake?pads?wear.?This?is?a?normal?condition?and?no?cause?for?concern.?If?the?level?drops?noticeably?over?ashort?period?of?time?or?goes?down?to?about?two?thirds?full,?have?your?brakes?checked?as?soon?as?possible.?Keep?the?reservoir?covered?except?for?the?amount?of?time?you?need?to?fill?it?and?never?leave?a?cam?of?brake?fluid?uncovered.Brake?fluid?must?maintain?a?very?high?boiling?point.?Exposure?to?air?will?cause?the?fluid?to?absorb?moisture?which?will?lower?that?boiling?point.?
??The?brake?fluid?travels?from?the?master?cylinder?to?the?wheels?through?a?series?of?steel?tubes?and?reinforced?rubber?hoses.?Rubber?hoses?are?only?used?in?places?that?require?flexibility,?such?as?at?the?front?wheels,?which?move?up?and?down?as?well?as?steer.?The?rest?of?the?system?uses?non-corrosive?seamless?steel?tubing?with?special?fittings?at?all?attachment?points.?If?a?steel?line?requires?a?repair,?the?best?procedure?is?to?replace?the?compete?line.?If?this?is?not?practical,?a?line?can?be?repaired?using?special?splice?fittings?that?are?made?for?brake?system?repair.?You?must?never?use?copper?tubing?to?repair?a?brake?system.?They?are?dangerous?and?illegal.?
Drum?brakes,?it?consists?of?the?brake?drum,?an?expander,?pull?back?springs,?a?stationary?back?plate,?two?shoes?with?friction?linings,?and?anchor?pins.?The?stationary?back?plate?is?secured?to?the?flange?of?the?axle?housing?or?to?the?steering?knuckle.?The?brake?drum?is?mounted?on?the?wheel?hub.?There?is?a?clearance?between?the?inner?surface?of?the?drum?and?the?shoe?lining.?To?apply?brakes,?the?driver?pushes?pedal,?the?expander?expands?the?shoes?and?presses?them?to?the?drum.?Friction?between?the?brake?drum?and?the?friction?linings?brakes?the?wheels?and?the?vehicle?stops.?To?release?brakes,?the?driver?release?the?pedal,?the?pull?back?spring?retracts?the?shoes?thus?permitting?free?rotation?of?the?wheels.?
Disk?brakes,?it?has?a?metal?disk?instead?of?a?drum.?A?flat?shoe,?or?disk-brake?pad,?is?located?on?each?side?of?the?disk.?The?shoes?squeeze?the?rotatin?g?disk?to?stop?the?car.?Fluid?from?the?master?cylinderforces?the?pistons?to?move?in,?toward?the?disk.?This?action?pushes?the?friction?pads?tightly?against?the?disk.?The?friction?between?the?shoes?and?disk?slows?and?stops?it.?This?provides?the?braking?action.?Pistons?are?made?of?either?plastic?or?metal.?There?are?three?general?types?of?disk?brakes.?They?are?the?floating-caliper?type,?the?fixed-caliper?type,?and?the?sliding-caliper?type.?Floating-caliper?and?sliding-caliper?disk?brakes?use?a?single?piston.?Fixed-caliper?disk?brakes?have?either?two?or?four?pistons.?
?The?brake?system?assemblies?are?actuated?by?mechanical,?hydraulic?or?pneumatic?devices.?The?mechanical?leverage?is?used?in?the?parking?brakes?fitted?in?all?automobile.?When?the?brake?pedal?is?depressed,?the?rod?pushes?the?piston?of?brake?master?cylinder?which?presses?the?fluid.?The?fluid?flows?through?the?pipelines?to?the?power?brake?unit?and?then?to?the?wheel?cylinder.?The?fluid?pressure?expands?the?cylinder?pistons?thus?pressing?the?shoes?to?the?drum?or?disk.?If?the?pedal?is?released,?the?piston?returns?to?the?initialposition,?the?pull?back?springs?retract?the?shoes,?the?fluid?is?forced?back?to?the?master?cylinder?and?braking?ceases.?
?The?primary?purpose?of?the?parking?brake?is?to?hold?the?vehicle?stationary?while?it?is?unattended.?The?parking?brake?is?mechanically?operated?by?the?driver?when?a?separate?parking?braking?hand?lever?is?set.?The?hand?brake?is?normally?used?when?the?car?has?already?stopped.?A?lever?is?pulled?and?the?rear?brakes?are?approached?and?locked?in?the?“on”?position.?The?car?may?now?be?left?without?fear?of?its?rolling?away.?When?the?driver?wants?to?move?the?car?again,?he?must?press?a?button?before?the?lever?can?be?released.?The?hand?brake?must?also?be?able?to?stop?the?car?in?the?event?of?the?foot?brake?failing. For?this?reason,?it?is?separate?from?the?foot?brake?uses?cable?or?rods?instead?of?the?hydraulic?system.?Anti-lock?Brake?System?
Anti-lock?brake?systems?make?braking?safer?and?more?convenient,?Anti-lock?brake?systems?modulate?brake?system?hydraulic?pressure?to?prevent?the?brakes?from?locking?and?the?tires?from?skidding?on?slippery?pavement?or?during?a?panic?stop.?
Anti-lock?brake?systems?have?been?used?on?aircraft?for?years,?and?some?domestic?car?were?offered?with?an?early?form?of?anti-lock?braking?in?late?1990’s.?Recently,?several?automakers?have?introduced?more?sophisticated?anti-lock?system.?Investigations?in?Europe,?where?anti-lock?brakin?g?systems?have?been?available?for?a?decade,?have?led?one?manufacture?to?state?that?the?number?of?traffic?accidents?could?be?reduced?by?seven?and?a?half?percent?if?all?cars?had?anti-lock?brakes.?So?some?sources?predict?that?all?cars?will?offer?anti-lock?brakes?to?improve?the?safety?of?the?car.?
?Anti-lock?systems?modulate?brake?application?force?several?times?per?second?to?hold?the?tires?at?a?controlled?amount?of?slip;?all?systems?accomplish?this?in?basically?the?same?way.?One?or?more?speed?sensors?generate?alternating?current?signal?whose?frequency?increases?with?the?wheel?rotational?speed.?An?electronic?control?unit?continuously?monitors?these?signals?and?if?the?frequency?of?a?signal?drops?too?rapidly?indicating?that?a?wheel?is?about?to?lock,?the?control?unit?instructs?a?modulating?device?to?reduce?hydraulic?pressure?to?the?brake?at?the?affected?wheel.?When?sensor?signals?indicate?the?wheel?is?again?rotating?normally,?the?control?unit?allows?increased?hydraulic?pressure?to?the?brake.?This?release-apply?cycle?occursseveral?time?per?second?to?“pump”?the?brakes?like?a?driver?might?but?at?a?much?faster?rate.?
In?addition?to?their?basic?operation,?anti-lock?systems?have?two?other?things?in?common.?First,?they?do?not?operate?until?the?brakes?are?applied?with?enough?force?to?lock?or?nearly?lock?a?wheel.?At?all?other?times,?the?system?stands?ready?to?function?but?does?not?interfere?with?normal?braking.?Second,?if?the?anti-lock?system?fail?in?any?way,?the?brakes?continue?to?operate?without?anti-lock?capability.?A?warning?light?on?the?instrument?panel?alerts?the?driver?when?a?problem?exists?in?the?anti-lock?system.?
?The?current?Bosch?component?Anti-lock?Braking?System?(ABSⅡ),?is?a?second?generation?design?wildly?used?by?European?automakers?such?as?BWM,?Mercedes-Benz?and?Porsche.?ABSⅡ?system?consists?of?:?four?wheel?speed?sensor,?electronic?control?unit?and?modulator?assembly.?A?speed?sensor?is?fitted?at?each?wheel?sends?signals?about?wheel?rotation?to?control?unit.?Each?speed?sensor?consists?of?a?sensor?unit?and?a?gear?wheel.?The?front?sensor?mounts?to?the?steering?knuckle?and?its?gear?wheel?is?pressed?onto?the?stub?axle?that?rotates?with?the?wheel.?The?rear?sensor?mounts?the?rear?suspension?member?and?its?gear?wheel?is?pressed?onto?the?axle.?The?sensor?itself?is?a?winding?with?a?magnetic?core.?The?core?creates?a?magnetic?field?around?the?winding,?and?as?the?teeth?of?the?gear?wheel?move?through?this?field,?an?alternating?current?is?induced?in?the?winding.?The?control?unit?monitors?the?rate?o?change?in?this?frequency?to?determine?impending?brake?lockup.?
?The?control?unit’s?function?can?be?divided?into?three?parts:?signal?processing,?logic?and?safety?circuitry.?The?signal?processing?sectionis?the?converter?that?receives?the?alternating?current?signals?form?the?speed?sensors?and?converts?them?into?digital?form?for?the?logic?section.?The?logic?section?then?analyzes?the?digitized?signals?to?calculate?any?brake?pressure?changes?needed.?If?impending?lockup?is?sensed,?the?logic?section?sends?commands?to?the?modulator?assembly.?Modulator?assembly?
The?hydraulic?modulator?assembly?regulates?pressure?to?the?wheel?brakes?when?it?receives?commands?from?the?control?utuit.?The?modulator?assembly?can?maintain?or?reduce?pressure?over?the?level?it?receives?from?the?master?cylinder,?it?also?can?never?apply?the?brakes?by?itself.?The?modulator?assembly?consists?of?three?high-speed?electric?solenoid?valves,?two?fluid?reservoirs?and?a?turn?delivery?pump?equipped?with?inlet?and?outlet?check?valves.?The?modulator?electrical?connector?and?controlling?relays?are?concealed?under?a?plastic?cover?of?the?assembly.?
Each?front?wheel?is?served?by?electric?solenoid?valve?modulated?independently?by?the?control?unit.?The?rear?brakes?are?served?by?a?single?solenoid?valve?and?modulated?together?using?the?select-low?principle.?During?anti-braking?system?operation,?the?control?unit?cycles?the?solenoid?valves?to?either?hold?or?release?pressure?the?brake?lines.?When?pressure?is?released?from?the?brake?lines?during?anti-braking?operation,?it?is?routed?to?a?fluid?reservoir.?There?is?one?reservoir?for?the?front?brake?circuit.?The?reservoirs?are?low-pressure?accumulators?that?store?fluid?under?slight?spring?pressure?until?the?return?delivery?pump?can?return?the?fluid?through?the?brake?lines?to?the?master?cylinder.
汽車制動(dòng)系統(tǒng)
制動(dòng)系統(tǒng)是汽車上最重要的系統(tǒng)。如果制動(dòng)系統(tǒng)壞了，結(jié)果會(huì)很嚴(yán)重。制動(dòng)器實(shí)際上是能量轉(zhuǎn)化裝置，制動(dòng)器能將車輛的動(dòng)能（動(dòng)量）轉(zhuǎn)化為熱能（熱）。當(dāng)司機(jī)踩制動(dòng)踏板時(shí)，司機(jī)施加的使汽車停下的力相當(dāng)于推動(dòng)汽車的力的十倍。制動(dòng)系統(tǒng)能施加在每個(gè)制動(dòng)器上的力有幾千磅。?
汽車上裝有兩套完全獨(dú)立的制動(dòng)系統(tǒng)，即行車制動(dòng)系統(tǒng)和駐車制動(dòng)系統(tǒng)?行車制動(dòng)用來減速、停車或者控制正在正常行駛的車輛，它是通過司機(jī)踩下和釋放剎車踏板來控制的。駐車制動(dòng)的主要目的是使車輛在無人看管時(shí)保持靜止?fàn)顟B(tài)。駐車制動(dòng)是機(jī)械式操作，司機(jī)可以通過一個(gè)獨(dú)立的駐車制動(dòng)剎車腳踏板或者剎車手柄來操控。?
制動(dòng)系統(tǒng)由下列基本部分組成：“制動(dòng)主缸”，安裝在發(fā)動(dòng)機(jī)罩的下面，直接與制動(dòng)踏板相連，將司機(jī)腳部的機(jī)械壓力轉(zhuǎn)化為液壓壓力。鋼制的“制動(dòng)管路”和柔韌的“制動(dòng)軟管”將制動(dòng)主缸與安裝在各個(gè)車輪上的“制動(dòng)輪缸”連接起來。制動(dòng)液，特別設(shè)計(jì)工作在極端環(huán)境下，充滿制動(dòng)系統(tǒng)。“制動(dòng)蹄”和“制動(dòng)襯塊”在制動(dòng)輪缸的推動(dòng)下分別與“制動(dòng)鼓”和“制動(dòng)盤”接觸而產(chǎn)生阻力，從而（有希望）使汽車減速。?
典型的制動(dòng)系統(tǒng)由前部的盤式制動(dòng)器和后部的盤式或鼓式制動(dòng)器組成，制動(dòng)器用管道與制動(dòng)主缸相連。?
基本上，所有的汽車制動(dòng)器都是摩擦式制動(dòng)器。當(dāng)司機(jī)開始制動(dòng)時(shí)，控制裝置迫使制動(dòng)蹄或者制動(dòng)襯塊擠壓車輪上的旋轉(zhuǎn)的制動(dòng)鼓或者制動(dòng)盤。制動(dòng)蹄與制動(dòng)鼓或者制動(dòng)襯塊與制動(dòng)盤之間的摩擦使車輪減速或者停下，從而使汽車被剎住。?
大多數(shù)現(xiàn)代制動(dòng)系統(tǒng)里都有一個(gè)充滿液體的缸體，叫做制動(dòng)主缸，它包含兩個(gè)獨(dú)立的部分，每個(gè)部分都有一個(gè)活塞，每個(gè)活塞都和司機(jī)駕駛室的剎車踏板相連。當(dāng)踩下制動(dòng)踏板時(shí)，制動(dòng)液就被從制動(dòng)主缸壓到各個(gè)車輪。?
在各個(gè)車輪處，制動(dòng)液推動(dòng)制動(dòng)蹄或制動(dòng)襯塊與旋轉(zhuǎn)的制動(dòng)鼓或制動(dòng)盤接觸。靜止的制動(dòng)蹄或制動(dòng)襯塊與轉(zhuǎn)動(dòng)的制動(dòng)鼓或制動(dòng)盤之間的摩擦，使制動(dòng)鼓或制動(dòng)盤減速或停止，這將使車輪減速或者停止，進(jìn)而使汽車減速或者停止。?
制動(dòng)液儲(chǔ)液罐在制動(dòng)主缸的頂部。今天大部分的汽車的制動(dòng)液儲(chǔ)液罐都是透明的，以便你不必打開蓋子就能看到液面的高度。制動(dòng)液的液面會(huì)隨著制動(dòng)襯塊的摩擦而下降，這是正常狀況不必?fù)?dān)心。如果液面高度在短時(shí)間內(nèi)明顯下降或者下降了三分之二，請(qǐng)盡快檢查你的制動(dòng)系統(tǒng)。保持制動(dòng)液儲(chǔ)液罐的蓋子是關(guān)閉狀態(tài)，除非你需要加油，絕不要讓凸輪制動(dòng)液暴漏著。制動(dòng)液必須保持非常高的沸點(diǎn)，暴漏在空氣中將造成制動(dòng)液吸收水分而沸點(diǎn)降低。?
制動(dòng)液通過一系列鋼制管路和強(qiáng)化的橡膠管從制動(dòng)主缸到達(dá)車輪處。橡膠管路僅僅用在對(duì)柔韌性有要求的地方，如前輪處，管路會(huì)隨著形式上下移動(dòng)。剩下的系統(tǒng)管路用不銹無縫鋼管通過特殊配件相連。如果鋼制管路需要修理，最好的方式是更換相同的管路，如果這不實(shí)際，也可以用為制動(dòng)系統(tǒng)維修專門生產(chǎn)的專用接頭配件來修理。決不能用銅制管路來維修制動(dòng)系統(tǒng)，那樣很危險(xiǎn)而且違反規(guī)定。?
鼓式制動(dòng)器，包括制動(dòng)鼓、一個(gè)制動(dòng)輪缸、回位彈簧、一個(gè)制動(dòng)底板、兩個(gè)帶摩擦片的制動(dòng)蹄和支承銷。制動(dòng)底板固定在驅(qū)動(dòng)橋殼的法蘭盤上或者轉(zhuǎn)向節(jié)上。制動(dòng)鼓安裝在輪轂上。制動(dòng)鼓的內(nèi)表面與制動(dòng)蹄摩擦片之間有一段間距。制動(dòng)時(shí)，司機(jī)踩下踏板，制動(dòng)輪缸是制動(dòng)蹄張開壓在制動(dòng)鼓上。制動(dòng)鼓與摩擦片之間的摩擦使車輪制動(dòng)，使車輛停止。解除制動(dòng)時(shí)，司機(jī)放開踏板，回位彈簧拉回制動(dòng)蹄從而使車輪能自由轉(zhuǎn)動(dòng)。?
盤式制動(dòng)器，有一個(gè)金屬盤代替了制動(dòng)鼓。制動(dòng)盤兩側(cè)各裝有一個(gè)平的制動(dòng)蹄或者叫盤式制動(dòng)摩擦襯塊。制動(dòng)襯塊擠壓旋轉(zhuǎn)的制動(dòng)盤使汽車停止。來自制動(dòng)主缸的制動(dòng)液迫使輪缸的活塞向制動(dòng)盤移動(dòng)，從而推動(dòng)摩擦襯塊緊緊地壓在制動(dòng)盤上。摩擦襯塊與制動(dòng)盤之間的摩擦使制動(dòng)盤減速和停止，這就是制動(dòng)的過程。活塞是塑料或者金屬制的。盤式制動(dòng)器有三種基本類型，浮鉗盤式制動(dòng)器、定鉗盤式制動(dòng)器和滑動(dòng)鉗盤式制動(dòng)器。浮鉗盤式制動(dòng)器和滑動(dòng)鉗盤式制動(dòng)器用一個(gè)活塞，定鉗盤式制動(dòng)器有兩個(gè)或者四個(gè)活塞。?
制動(dòng)系統(tǒng)裝配組件驅(qū)動(dòng)方式有機(jī)械式、液壓式或者氣壓式。機(jī)械式杠桿機(jī)構(gòu)適用于所有汽車的駐車制動(dòng)。當(dāng)踩下制動(dòng)踏板時(shí)，推桿推動(dòng)制動(dòng)主缸的活塞移動(dòng)，制動(dòng)液從油管流到動(dòng)力制動(dòng)單元再流到制動(dòng)輪缸，制動(dòng)液的壓力推開輪缸的活塞，從而使摩擦片擠壓制動(dòng)鼓或制動(dòng)盤。如果放開制動(dòng)踏板，活塞回到初始位置，回位彈簧使制動(dòng)蹄回位，制動(dòng)液被壓回主缸，制動(dòng)停止。?
駐車制動(dòng)的主要作用是使車輛在無人看管時(shí)保持靜止，駐車制動(dòng)是機(jī)械式操作，司機(jī)通過一個(gè)獨(dú)立的制動(dòng)手柄來操縱。手剎通常在汽車已經(jīng)停下時(shí)使用。當(dāng)拉動(dòng)手剎時(shí)，后制動(dòng)系統(tǒng)被剎住并被鎖在“打開”的位置，現(xiàn)在可以把汽車扔下而不用擔(dān)心它自己移走了。當(dāng)司機(jī)想要再次移動(dòng)汽車時(shí)，他必須按一個(gè)按鈕才能使手剎拉桿松開。手剎還必須能在腳剎失靈的情況下使汽車停止，因此，手剎系統(tǒng)采用拉索或杠桿，不同于腳剎采用液壓系統(tǒng)。?
防抱死制動(dòng)系統(tǒng)使制動(dòng)更加安全和方便，防抱死制動(dòng)系統(tǒng)調(diào)節(jié)制動(dòng)系統(tǒng)液壓，防止制動(dòng)器鎖死，防止輪胎在光滑路面上或緊急制動(dòng)時(shí)發(fā)生打滑。?
防抱死制動(dòng)系統(tǒng)已經(jīng)用在航空飛行器上多年，90年代末期，一些中國(guó)產(chǎn)汽車裝備了早期形式的防抱死制動(dòng)系統(tǒng)?，F(xiàn)在，一些汽車制造商已經(jīng)引進(jìn)了更先進(jìn)的防抱死制動(dòng)系統(tǒng)。在防抱死制動(dòng)系統(tǒng)已經(jīng)應(yīng)用十年的歐洲進(jìn)行的一項(xiàng)調(diào)查說明，如果所有的車都有防抱死制動(dòng)系統(tǒng)，交通事故的數(shù)量將可以減少7.5%，所以一些人預(yù)計(jì)將來所有的車都會(huì)裝上防抱死制動(dòng)系統(tǒng)，以提高汽車的安全性。?
防抱死系統(tǒng)每秒調(diào)節(jié)制動(dòng)作用力幾次，以把輪胎的滑移量控制在一定范圍內(nèi)；基本上所有的系統(tǒng)都是以這種方式來完成的。一個(gè)或多個(gè)速度傳感器產(chǎn)生交流信號(hào)，交流信號(hào)的頻率隨著車輪轉(zhuǎn)速的提高而增大一個(gè)電控單元不斷監(jiān)測(cè)著這些信號(hào)，如果其中一個(gè)信號(hào)的頻率下降的太迅速，表明一個(gè)車輪將要抱死，電控單元命令調(diào)節(jié)裝置減小受影響車輪的制動(dòng)液壓。當(dāng)傳感器信號(hào)表明車輪仍在正常轉(zhuǎn)動(dòng)時(shí)，控制單元允許制動(dòng)器增大液壓，這種收放循環(huán)每秒發(fā)生幾次，對(duì)制動(dòng)器的控制類似于司機(jī)反復(fù)釋放和踩下踏板，但是速度更快。?
除了他們的基本作用，關(guān)于防抱死系統(tǒng)還有另外兩件事。第一，防抱死系統(tǒng)直到制動(dòng)器抱死車輪才起作用，在其他時(shí)間，防抱死系統(tǒng)做好運(yùn)行的準(zhǔn)備，但是不干涉正常制動(dòng)。第二，如果防抱死系統(tǒng)失靈了，制動(dòng)器沒有了防抱死能力仍然能繼續(xù)工作，當(dāng)防抱死系統(tǒng)存在問題時(shí)，儀表盤上的一個(gè)警示燈會(huì)提示司機(jī)。?
歐洲汽車制造商，如寶馬、奔馳和保時(shí)捷，廣泛使用的是博世的第二代防抱死制動(dòng)系統(tǒng)ABSⅡ。ABSⅡ系統(tǒng)包括：四個(gè)車輪轉(zhuǎn)速傳感器、電子控制單元和調(diào)節(jié)裝置。?
裝在每個(gè)車輪上的輪速傳感器將車輪轉(zhuǎn)動(dòng)信號(hào)送到控制單元，每個(gè)速度傳感器包括一個(gè)磁感應(yīng)傳感頭和一個(gè)齒圈。前輪傳感器安裝在轉(zhuǎn)向節(jié)上，它的齒圈安在轉(zhuǎn)向軸上，隨車輪一起旋轉(zhuǎn)。后傳感器安裝在后懸架部件上，它的齒圈安裝在車軸上。傳感器是一個(gè)有磁芯的線圈，磁芯產(chǎn)生一個(gè)環(huán)繞線圈的磁場(chǎng)，當(dāng)齒圈的齒穿過磁場(chǎng)時(shí)，線圈中會(huì)產(chǎn)生交流電。控制單元監(jiān)測(cè)著頻率變化的速度，以判斷什么時(shí)候即將抱死。?
控制單元的作用可以分為三部分：信號(hào)處理，邏輯計(jì)算和安全電路。信號(hào)處理部分是將從輪速傳感器接收到的交流信號(hào)轉(zhuǎn)換成數(shù)字形式，為邏輯計(jì)算做準(zhǔn)備。然后邏輯計(jì)算部分分析這些數(shù)字化的信號(hào)，計(jì)算出制動(dòng)壓力需要的改變。如果覺察到即將抱死，邏輯計(jì)算部分將向液壓調(diào)節(jié)器發(fā)出命令。?
當(dāng)液壓調(diào)節(jié)器接受到控制單元的命令時(shí)，將會(huì)調(diào)節(jié)車輪制動(dòng)器中的液壓。液壓調(diào)節(jié)器能保持或者減少來自制動(dòng)主缸的壓力，但是它不能自己?jiǎn)?dòng)制動(dòng)器。液壓調(diào)節(jié)器包括三個(gè)高速的電磁閥、兩個(gè)儲(chǔ)液器和一個(gè)裝有進(jìn)出口止回閥的輸出泵。調(diào)節(jié)器的電子連接器和控制繼電器隱蔽在塑料蓋子下。?
每個(gè)前輪都有一個(gè)電磁閥，受控制單元獨(dú)立調(diào)節(jié)。兩個(gè)后輪則只有一個(gè)電磁閥，采用低選擇原則共同調(diào)節(jié)。在防抱死制動(dòng)系統(tǒng)起作用時(shí)，控制單元循環(huán)控制電磁閥保持或者減小制動(dòng)系統(tǒng)的液壓，當(dāng)防抱死期間制動(dòng)系統(tǒng)液壓被降低時(shí)，制動(dòng)液被壓入儲(chǔ)液器。前制動(dòng)線路有一個(gè)儲(chǔ)液罐。儲(chǔ)液罐是低壓蓄能器，在低壓下儲(chǔ)存油液，直到回流泵將油液從管路送回制動(dòng)主缸。
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