汽車液壓制動驅動機構的設計【桑塔納汽車制動驅動結構的設計】

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河北科技師范學院 畢業(yè)論文（設計）文獻綜述 題 目： 液壓制動系統(tǒng)的發(fā)展 學 生 姓 名： 張海燕 指 導 教 師： 鄭立新 系 別： 機械電子系 專業(yè) 、班級： 機械設計制造及自動化0204班 完 成 時 間： 2005年12月23日 河北科技師范學院教務處制 汽車液壓制動系統(tǒng)的發(fā)展 張海燕 （河北科技師范學院 機械電子系 機械設計制造及其自動化） 摘要:闡述了汽車制動控制統(tǒng)統(tǒng)的歷史、現(xiàn)狀和發(fā)展趨勢,著重分析了人力液壓制動系統(tǒng)的工作原理,討論了ABS防抱死系統(tǒng)的魯棒性和BBW系統(tǒng)的基本原理,介紹了液壓制動系統(tǒng)中液壓油的使用要求。 關鍵詞:制動系統(tǒng);制動缸;制動控制　 　　　　 從汽車自問世以來,制動系統(tǒng)在車輛行車和駐車的安全方面扮演著至關重要的角色.近年來,隨著車輛技術的進步和汽車行駛速度的提高,這種重要性表現(xiàn)得越來越明顯.眾多的汽車工程師在改進汽車制動性能的研究中傾注了大量的心血.目前關于汽車制動的研究主要集中在制動控制方面[1],包括制動控制的理論和方法,以及新技術推廣應用.。 1．制動系統(tǒng)的歷史 對汽車的制動作用.由于那時的車輛的重量比較小,速度比較低,機械制動也能滿足車輛制動的需要,但隨著汽車自身重量的增加,助力裝置對機械制動器來說已顯得十分必要.于是開始出現(xiàn)了真空助力裝置.1932年生產的質量為2860kg的凱迪拉克轎車四輪采用直徑419.1mm的鼓式制動器,并有制動踏板控制的真空助力裝置.林肯公司也在同年推出同種類型的轎車,該車采用了通過四根軟索控制真空助力器的鼓式制動器[2]. 隨著科學技術的發(fā)展及汽車工業(yè)的發(fā)展,尤其是軍用車輛及軍用技術的發(fā)展,車輛制動有了新的突破,液壓制動是繼機械制動后的又一重大突破.DuesenbergEight車率先使用了轎車液壓制動器.克萊斯勒的四輪液壓制動器于1924年問世.通用和福特分別于1934年和1939年采用了液壓制動技術.到20世紀50年代,液壓助力制動器開始在制動系統(tǒng)中應用[3]. 20世紀30年代后期,隨著電子技術的發(fā)展,世界汽車技術領域最顯著的成就是ABS防抱死制動系統(tǒng)(antilockbrakingsystem)[1]的使用和推廣.ABS集微電子技術、精密加工技術、液壓控制技術為一體,是機電一體化的高技術產品.它的使用大大提高了汽車的主動安全性和操縱性.防抱死控制裝置一般包括三部分:傳感器、控制器(ABSECU)與壓力調節(jié)器.傳感器接受運動參數(shù),如車輪角速度、角加速度、車速等傳送給控制裝置,控制裝置進行計算并與規(guī)定的數(shù)值進行比較后,給壓力調節(jié)器發(fā)出指令. 1936年,博世公司申請一項電液控制的ABS裝置專利,促進了防抱死制動系統(tǒng)在汽車上的應用.1969年福特使用了真空助力的ABS制動器;1971年,克萊斯勒車采用了四輪電子控制的ABS裝置.這些早期的ABS裝置性能有限,可靠性不夠理想,且成本高. 1979年,默·本茨推出了一種性能可靠、帶有獨立液壓助力器的全數(shù)字電子系統(tǒng)控制的ABS制動裝置.1985年美國開發(fā)出帶有數(shù)字顯示微處理器、復合主缸、液壓制動助力器、電磁閥及執(zhí)行器“一體化”的ABS防抱死裝置.隨著大規(guī)模集成電路和超大規(guī)模集成電路技術的出現(xiàn),以及電子信息處理技術的高速發(fā)展,ABS已成為性能可靠、成本日趨下降的具有廣泛應用前景的成熟產品.一些國家和地區(qū)(如歐洲、日本、美國等)已制定法規(guī),使ABS成為汽車的標準設備[4]. 2.制動控制系統(tǒng)的發(fā)展現(xiàn)狀 傳統(tǒng)的制動控制系統(tǒng)的主要特點是能均勻分配油液壓力.當制動踏板踏下時,制動主缸就將等量的油液送到每個制動器的制動輪缸中,并通過一個比例閥使前后平衡.而ABS或其他制動干預系統(tǒng)則根據(jù)每個制動器的需要對油液壓力進行調節(jié).目前ABS系統(tǒng)已發(fā)展成為成熟的產品,并在各種車輛上得到了廣泛的應用,但是這些產品基本都是基于車輪加、減速門限及參考滑移率方法設計的.方法雖然簡單實用,但是其調試比較困難,不同的車輛需要不同的匹配技術,在許多不同的道路上加以驗證. 制動控制系統(tǒng)的重要問題在于控制的穩(wěn)定性,即系統(tǒng)魯棒性(robustness),應保證在各種條件下制動系統(tǒng)的控制作用不失效.防抱死系統(tǒng)要求高可靠性,否則會導致人身傷亡及車輛損壞.因此,發(fā)展魯棒性的ABS控制系統(tǒng)成為關鍵所在.現(xiàn)在,多種魯棒控制系統(tǒng)都應用到ABS的控制邏輯中來[4].除了傳統(tǒng)的邏輯門限方法外,增益調度PID控制、變結構控制和模糊控制是常用的魯棒控制系統(tǒng),是目前所采用的以滑移率為目標的連續(xù)控制系統(tǒng).模糊控制法是基于經(jīng)驗規(guī)則的控制,與系統(tǒng)的模型無關,具有很好的魯棒性和控制規(guī)則的靈活性,但調整控制參數(shù)比較困難,尚無理論計算公式,基本上是靠試湊的方法.然而對大多數(shù)基于目標值的控制而言,控制規(guī)律有一定的規(guī)律. 車輪的驅動打滑與制動抱死是很類似的問題.在汽車起動或加速時,因驅動力過大而使驅動輪高速旋轉、超過摩擦極限而引起打滑.此時,車輪同樣不具有足夠的側向力來保持車輛的穩(wěn)定,車輪切向力也減少,影響加速性能.由此看出,防止車輪打滑與抱死都是要控制汽車的滑移率,所以在ABS的基礎上發(fā)展了驅動防滑系統(tǒng)(ASR)[6].ASR是ABS的邏輯和功能擴展.ABS在增加了ASR功能后,主要的變化是在電子控制單元中增加了驅動防滑邏輯系統(tǒng),來監(jiān)測驅動輪的轉速.ASR大多借用ABS的硬件,兩者共存一體,發(fā)展成為ABS/ASR系統(tǒng). 今天,ABS/ASR已經(jīng)成為歐美和日本等發(fā)達國家汽車的標準設備,并且已在歐洲新載貨車中普遍使用,歐共體法規(guī)EEC/71/320已強制性規(guī)定在總質量大于3.5t的某些載貨車上使用,重型車輛首先裝用的.隨著技術的成熟和發(fā)展,現(xiàn)在的高級轎車也開始采用ABS/ASR系統(tǒng).然而ABS/ASR只是解決了緊急制動時附著系數(shù)的利用,可獲得較短的制動距離及制動方向穩(wěn)定性,但是不能解決制動系統(tǒng)中的所有缺陷. 3.制動控制系統(tǒng)的發(fā)展趨勢 經(jīng)過一百多年的發(fā)展,汽車制動系統(tǒng)的結構已經(jīng)基本固定下來.隨著電子技術,特別是大規(guī)模、大規(guī)模集成電路的發(fā)展,汽車制動系統(tǒng)的形式也將發(fā)生變化.凱西-海斯(K-H)公司在一輛實驗車上安裝了一種電-液(EH)制動系統(tǒng),該系統(tǒng)徹底改變了制動系統(tǒng)的工作原理.通過采用4個比例閥和電力電子控制裝置,該系統(tǒng)能處理基本制動、ABS、牽引力控制、巡航控制制動干預等情況,而不需增加任何一種附加裝置.該系統(tǒng)潛在的優(yōu)點是比標準制動器能更加有效地分配基本制動力,從而使制動距離縮短5%.一種完全無油液、完全通過電路控制的BBW(Brake-By-Wire)[7]系統(tǒng)的開發(fā)將使傳統(tǒng)的液壓制動控制系統(tǒng)成為歷史. BBW系統(tǒng)是未來制動控制系統(tǒng)的發(fā)展方向.全電制動系統(tǒng)不同于傳統(tǒng)的制動系統(tǒng),因為其傳遞的是電流,而不是液壓油或壓縮空氣,可以省去許多管路和傳感器,縮短制動反應時間. 4.汽車制動液的使用 制動液是液壓制動系統(tǒng)的重要組成部分,它的質量好壞對制動系統(tǒng)的工作可靠性有很大的影響.因此制動液應具有高溫下不易液化、低溫下流動性良好、吸水性差而溶水性良好、能潤滑液壓系統(tǒng)的運動件而不會使其腐蝕,不會使橡膠件發(fā)生膨脹、變硬和損壞等特點. 在選用制動液時應根據(jù)制動系統(tǒng)是否安裝ABS裝置來選擇.因為沒有安裝ABS的車輛在緊急制動時往往會使車輪抱死,安裝ABS后,可使汽車在緊急制動時車輪不會被抱死而防止出現(xiàn)側滑,因此ABS裝置工作時,制動系統(tǒng)產生的摩擦熱比未裝ABS裝置的車高,制動液的惡化變質也會相對早地出現(xiàn),適合于ABS的只能是高沸點的制動液,如果使用低沸點的制動液,會因容易產生氣阻而使汽車處于非常危險的狀態(tài). 如果在制動液變質的情況下繼續(xù)使用,將會使制動主缸、制動輪缸、油壓控制器等產生損傷、吸濕率增加,使制動力下降[8].因此,要對裝有ABS裝置車輛的制動液進行從嚴選用,嚴格遵守汽車制造廠商推薦的更換周期.另外還要根據(jù)使用條件,在必要時提前進行更換. 6.結束語 介紹汽車制動控制系統(tǒng)的進展歷史,詳細闡述制動控制系統(tǒng)由簡單的機械制動裝置發(fā)展到ABS防抱死制動控制系統(tǒng),可以嘗試模糊控制方法以改進汽車控制系統(tǒng)的性能.現(xiàn)代汽車制動控制技術正朝著電子制動控制方向發(fā)展.全電制動控制因其巨大的優(yōu)越性,將取代傳統(tǒng)的以液壓為主的傳統(tǒng)制動控制系統(tǒng).同時,隨著其他汽車電子技術特別是超大規(guī)模集成電路的發(fā)展,電子元件的成本及尺寸不斷下降.另外汽車電子制動控制系統(tǒng)將與其他汽車電子系統(tǒng)融合在一起成為綜合的汽車電子控制系統(tǒng),未來的汽車中就不存在孤立的制動控制系統(tǒng),各種控制單元集中在一個ECU中,并將逐漸代替常規(guī)的控制系統(tǒng),實現(xiàn)車輛控制的智能化. 參考文獻： [1]SchinkelM.Anti-lockbrakingcontrolusingaslidingmodelikeapproach[J].ProceedingsoftheAmericanControlConference,2002,(3):23862391. [2]KazemiR.DevelopmentofanewABSforpassengercarsusingdynamicsurfacecontrolmethod[J].ProceedingsoftheAmericanControlConference,2001,(2):677683. [3]　陳家瑞.汽車構造[M].北京:機械工業(yè)出版社,2000. [4]　沙奇林.ABS控制邏輯對車輛動力學模型參數(shù)及滑移率的規(guī)避分析[J].汽車工程,1996,16(6):329333. [5]　陳軍.防抱死制動系統(tǒng)不同控制方法的模擬研究[J].汽車技術,1989,(11):2326. [6]　馬岳軍.基于ABS的ABSASR集成液壓系統(tǒng)設計[J].液壓與氣動,2004,(6):2729. [7] 戴冠軍、周軍、孫偉等[M]汽車底盤維修大全 –杭州：浙江科學技術出版社 2000.4 [8] 張大成、戴波南等 [M] 上海桑塔納2000系列轎車維修手冊 –北京:北京理工大學出版社 2001.12 [9]ParkShinsuk.Numericalevaluationofbrakingfeeltodesignoptimalbrake-by-wiresystem[J].InternationalJournalofVehicleDesign,2005,37(1):123. [10] 陳家瑞等 汽車構造 [M] -北京：人民交通出版社20 Automobile hydraulic brake system development Zhang Haiyan (Dept.of Machinery and Electron,Hebei Normal University of Science & Technology) Abstract: Elaborated the automobile brake control entirely history, the present situation and the trend of development, have emphatically analyzed the manpower hydraulic brake system principle of work, discussed ABS to guard against holds the dead system robustness and the BBW system basic principle, introduced in the hydraulic brake system the hydraulic fluid operation requirements. Key words: Braking system; Applies the brake the cylinder;　 　　　　 5 The Brake System http://www.vibig.net/ The braking system is the most important system in your car. If your brakes fail, the result can be disastrous. Brakes are actually energy conversion devices, which convert the kinetic energy (momentum) of your vehicle into thermal energy (heat). When you step on the brakes, you command 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. In modern systems, the master cylinder is power-assisted by the engine. All newer cars have dual systems, with two wheels' brakes operated by each subsystem. That way, if one subsystem fails, the other can provide reasonably adequate braking power. Safety systems like this make modern brakes more complex, but also much safer than earlier braking systems. 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 your 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. In recent years, brakes have changed greatly in design. Disc brakes, used for years for front wheel applications, are fast replacing drum brakes on the rear wheels of modern cars. This is generally due to their simpler design, lighter weight and better braking performance. The greatest advantage of disc brakes is that they provide significantly better resistance to "brake fade" compared to drum type braking systems. Brake fade is a temporary condition caused by high temperatures generated by repeated hard braking. It occurs when the pads or shoes "glaze" due to the great pressure and heat of hard use. Once they cool, the condition subsides. Disc brakes allow greater air ventilation (cooling) compared to drum brakes. Drum brakes are not internally ventilated because if they were, water could accumulate in them. Disc brakes can rapidly fling off any water that they are exposed to, and so they can be well ventilated. "Boosters" are present in "power brake" systems, and use the engine's energy to add pressure to the master cylinder. "Anti-lock" (ABS) systems, originally developed for aircraft braking systems, use computer controlled valves to limit the pressure delivered to each slave cylinder. If a wheel locks up, steering input cannot affect the car's direction. With ABS, no matter how hard the pedal is pressed, each wheel is prevented from locking up. This prevents skidding (and allows the driver to steer while panic-braking). As impressive as these advances are, the basic process of converting a vehicle's momentum into (wasted) heat energy has not changed since the days of the horse and buggy. To stop a horse drawn carriage, the driver would pull on a lever which would rub on the wheel. But today, with the advent of regenerating brakes on electric vehicles, new ways of recapturing this lost energy are being developed. In these types of electric cars, when you step on the brakes, the motor switches into "generator mode", and stores the car's momentum as chemical energy in the battery, to be used again when the light turns green! Disc Brakes Disc brakes use a clamping action to produce friction between the "rotor" and the "pads" mounted in the "caliper" attached to the suspension members. Inside the calipers, pistons press against the pads due to pressure generated in the master cylinder. The pads then rub against the rotor, slowing the vehicle. Disc brakes work using much the same basic principle as the brakes on a bicycle; as the caliper pinches the wheel with pads on both sides, it slows the bicycle. Disc brakes offer higher performance braking, simpler design, lighter weight, and better resistance to water interference than drum brakes. Disc brakes, like many automotive innovations, were originally developed for auto racing, but are now standard equipment on virtually every car made. On most cars, the front brakes are of the disc type, and the rear brakes are of the "drum" type. Drum brakes use two semi-circular shoes to press outward against the inner surfaces of a steel drum. Older cars often had drum brakes on all four wheels, and many new cars now have 4-wheel disc brakes. Because disc brakes can fling off water more easily than drum brakes, they work much better in wet conditions. This is not to say that water does not affect them, it definitely does. If you splash through a puddle and then try to apply the brakes, your brakes may not work at all for a few seconds! Disc brakes also allow better airflow cooling, which also increases their effectiveness. Some high performance disc brakes have drilled or slotted holes through the face of the rotor, which helps to prevent the pads from "glazing" (becoming hardened due to heat). Disc brakes were introduced as standard equipment on most cars in the early seventies. Brake Drums The brake drum is a heavy flat-topped cylinder, which is sandwiched between the wheel rim and the wheel hub. The inside surface of the drum is acted upon by the linings of the brake shoes. When the brakes are applied, the brake shoes are forced into contact with the inside surface of the brake drums to slow the rotation of the wheels. The drums are usually covered with fins on their outer surfaces to increase cooling. They are not cooled internally, because water could enter through the air vent cooling holes and braking would then be greatly impaired. Drum brakes are found on the rear wheels of most older cars, but they are increasingly being fazed out in favor of rear disc brakes. Drum brakes were standard equipment on all four wheels of most cars until the early 70's. Brake Calipers The caliper works like a C-clamp to pinch the pads onto the rotor. It straddles the rotor and contains the hydraulic "slave cylinder" or "wheel cylinder" piston(s). One caliper is mounted to the suspension members on each wheel. The caliper is usually mounted onto the spindle, allowing it to deliver the torsional force of the wheel to the chassis via the control arms. Brake hoses connect the caliper to the brake lines leading to the master cylinder. A "bleeder valve" is located on each caliper to allow air bubbles to be purged from the system. "Floating caliper" disc brakes, the most common variety, allow the caliper to move from side to side slightly when the brakes are applied. This is because only one pad moves (in relation to the caliper). Some calipers contain two or four seperate pistons. These calipers are fixed in place; i.e., there is no lateral movement like the floating caliper, the pistons take up the slack on each side of the rotor. These are called "dual cylinder" or "dual piston" calipers, and are standard equipment on many performance cars. Wheel (Slave) Cylinder Wheel cylinders, also called the "slave" cylinders, are cylinders in which movable piston(s) convert hydraulic brake fluid pressure into mechanical force. Hydraulic pressure against the piston(s) within the wheel cylinder forces the brake shoes or pads against the machined surfaces of the drum or rotor. There is one cylinder (or more in some systems) for each wheel. Drum brake wheel cylinders are usually made up of a cylindrical casting, an internal compression spring, two pistons, two rubber cups or seals, and two rubber boots to prevent entry of dirt and water. This type of wheel cylinder is fitted with push rods that extend from the outer side of each piston through a rubber boot, where they bear against the brake shoes. In disc brakes, the wheel cylinder is built into the caliper. All wheel cylinders have bleeder screws (or bleeder valves) to allow the system to be purged of air bubbles. As the brake pedal is depressed, it moves pistons within the master cylinder, pressurizing the brake fluid in the brake lines and slave cylinders at each wheel. The fluid pressure causes the wheel cylinders' pistons to move, which forces the shoes or pads against the brake drums or rotors. Drum brakes use return springs to pull the pistons back away from the drum when the pressure is released. On disc brakes, the calipers' piston seals are designed to retract the piston slightly, thus allowing the pads to clear the rotor and thereby reduce rolling friction. Parking (Emergency) Brakes The parking brake (sometimes called the emergency brake) is a cable-activated system used to hold the brakes continuously in the applied position. The parking brake activates the brakes on the rear wheels. Instead of hydraulic pressure, a cable (mechanical) linkage is used to engage the brake shoes or discs. When the parking-brake pedal is pressed (or, in many cars, a hand lever is pulled), a steel cable draws the brake shoes or pads firmly against the drums or rotors. The release lever or button slackens the cables and disengages the brake shoes. The parking brake is self adjusting on most systems. An automatic adjuster compensates for lining (brake shoe) wear. On many cars, the parking brake is used to re-adjust the brake shoes as they wear in, or when the shoes are replaced. In these systems, the adjustment is made by repeatedly applying the parking brake while backing up. The parking brake can be useful while driving up hills: If you're driving a manual transmission car, and you pull up to a stop on an incline, you might notice that you don't have enough feet to operate the clutch, brake, and gas at the same time. In other words, you will likely roll backwards slightly while getting started again. If a someone pulls up right behind you, this can be a problem. Your parking brake is useful in this situation: Apply the parking brake after you stop. When you want to go, release the clutch while pressing the gas, and release the parking brake. This keeps you from having to quickly switch your left foot from the brake to the clutch, or your right foot from the brake to the gas pedal. A little practice, and you'll be able to do it smoothly. Also, remember if you pull up behind someone who is stopped on a hill, give them extra room to roll back a little. Especially if it's a truck. Some cars have no parking brake release! They automatically release the parking brake when the car is placed in drive or reverse. Remember, it's a good idea to test the parking brake periodically and keep it in good condition. It may save your life if the main braking system fails! http://www.vibig.net/Article_Show.asp?ArticleID=689