畢業(yè)設(shè)計英文翻譯-制動系統(tǒng)

1、harbin institute of technology本科畢業(yè)論文（設(shè)計）翻譯資料論文題目 解放j6載貨車制動系統(tǒng)設(shè)計班級 姓名 院（系）汽車工程學(xué)院 導(dǎo)師制動系統(tǒng)制動系統(tǒng)是如何工作的制動系統(tǒng)是利用摩擦來降低車輪的運動的。現(xiàn)在主要有兩種制動系統(tǒng)， abs和無abs系統(tǒng)（制動防滑）。其中一個系統(tǒng)是基于液壓裝置，和制動主缸（連 接到車內(nèi)的制動踏板）配合，制動主缸將制動液壓傳到前后制動卡鉗或制動 缸。鼓式制動器鼓式制動器的制動是由一組制動蹄或者制動襯片壓緊旋轉(zhuǎn)制動鼓的內(nèi)表 面而引起的摩擦。制動鼓和旋轉(zhuǎn)的車輪相連接。歷史現(xiàn)代汽車鼓式制動器是由路易斯雷諾在1902年發(fā)明的，盡管邁巴赫公司 在一年前

2、就使用了一種不太復(fù)雜的鼓式制動器。在第一例鼓式制動器中，制 動蹄是由杠桿，木棒或者纜繩機械操縱的。從19世紀30年代中期制動蹄由 一個小的輪缸和活塞驅(qū)動，但還是有些車輛繼續(xù)使用純機械操縱系統(tǒng)幾十年。 有些設(shè)計有兩個輪缸。鼓式制動器的制動蹄受到磨損，制動器需要定期調(diào)整， 直到19世紀50年代自動調(diào)節(jié)鼓式制動器的出現(xiàn)。19世紀六七十年代，汽車 前輪的制動鼓逐漸被盤式制動器所取代，現(xiàn)在幾乎所有汽車前輪都是盤式制 動器，有些甚至所有車輪都是盤式制動器。然而,鼓式制動器仍經(jīng)常用于手剎 制動，事實證明盤式制動器在讓汽車駐車時很難設(shè)計。此外，在盤式制動器中 很容易安裝一個手制動鼓，這樣就可以讓一個裝置在腳制

3、動和手制動時都可 以發(fā)揮作用。早期生產(chǎn)的制動蹄包含石棉。在修理老式汽車的制動系統(tǒng)時，必 須注意不耍吸入剎車總成中的灰塵。聯(lián)邦政府開始控制石棉生產(chǎn)，以致有一段 時間,車主們都在抱怨無石棉制動摩擦襯片帶來的低下的制動效果。最終由于 先進技術(shù)的發(fā)展，大多數(shù)老款汽車的駕駛者都裝了無石棉的摩擦襯片。伺服系統(tǒng)設(shè)計鼓式制動器，由于制動蹄較接的方式，可以有一個“自動伺服”的特點。這 使得在不增加駕駛者額外體力的情況下增加制動力，因為旋轉(zhuǎn)的制動鼓會拖 拽周圍的制動蹄，從而加大了使他們靠在一起的力。在后制動器上只有一個 蹄有這樣的特性。（前鼓式制動器也可能使用兩個驅(qū)動輪缸，這樣兩個蹄都可 以利用伺服特性了，當然這

4、也增加了前軸制動力，需要彌補向前轉(zhuǎn)移的載荷, 與此同時也要避免后輪提前抱死。伺服現(xiàn)象可以用來制造一個非常大的制動 作用（如大型商用車輛的后軸），但它確實降低了司機對制動的敏感度。（盤式制 動器由于襯塊垂直地作用于制動盤而沒有自動伺服效果）。優(yōu)勢鼓式制動器仍使用在現(xiàn)代汽車中，因為它在技術(shù)和成本方面更占優(yōu)勢。 駐車制動時用鼓式制動器結(jié)構(gòu)簡單。他們通常應(yīng)用于后輪，因為大部分制動 作用是由前輪產(chǎn)生的，因此后輪制動產(chǎn)生的熱量明顯減少。鼓式制動器有時也 安裝在后輪以盤式制動器作為主耍剎車的汽車上，起到駐車和緊急制動的作 用。在這種情況下，小型制動鼓通常是安裝在剎車盤上或直接作為剎車盤的一 部分。豐田普銳斯

5、，一款技術(shù)先進的混合動力汽車，其后輪就采用鼓式制動器。 （4輪皆盤式使用在一些特定市場一一混合動力汽車依靠能量回收，電動發(fā)電 機，可見再生制動技術(shù)等大大減少日常制動系統(tǒng)的磨損）。缺點鼓式制動器內(nèi)部的制動蹄有一個特定的缺點：長時間急劇制動時會使得 制動鼓溫度升高，其直徑會由于材料的膨脹而變大，制動蹄必須被更用力的 壓緊來獲得有效的制動作用。這被稱為制動失效,可能導(dǎo)致司機恐慌，極端情 況下甚至導(dǎo)致制動失效。在正常駕駛條件下，很少被注意到，特別是安裝的制 動鼓尺寸適宜的時候。龐蒂亞克gto的汽車因其使用較小尺寸的制動鼓而常 被人們提起。剎車片在嵌入剎車片過程中，將高摩擦的剎車片材料嵌入到制動盤中，同

6、事保 證磨損均勻。雖然人們普遍認為是剎車片材料與制動盤表面金屈接觸才使汽 車停下的，但其實是剎車片內(nèi)部一層很薄的材料產(chǎn)生了半液體摩擦邊界，從 而產(chǎn)生了實際的制動力。當然，制動盤磨損的快慢取決于所用材料的特性。 材料磨損特性的好壞是由性能和壽命之間的權(quán)衡來判定的。剎車片必須定期更換，大多數(shù)汽車都安裝了報警裝置，提醒駕駛者該更 換剎車片了。有的是利用一片薄金屬片，當剎車片變得太薄時，引起制動尖叫。另一些將薄金展片嵌入剎車片材料中，當剎車片變太薄時，會關(guān)閉電路, 并點亮警示燈。更高級的汽車可能會使用電子傳感器。雖然幾乎所有的公路 車輛每個制動鉗僅有兩個制動襯塊，但賽車卡鉗可利用多達6個制動襯塊， 將

7、不同的摩擦特性交錯布置，以獲得最佳的性能。早期的制動襯塊和制動蹄 含有石棉。當修理老式汽車的制動器時，一定要小心，不要吸入制動鉗或制 動鼓中的灰塵。制動尖叫有時當施加制動時，會出現(xiàn)很大的噪聲或者是高音調(diào)的尖叫。大部分制 動尖叫是由于制動器部件尤其是制動襯塊和制動盤的振動（共振不穩(wěn)定）產(chǎn) 生的。這種類型的制動尖叫不會對制動效能產(chǎn)生負面影響。一些簡單的技術(shù), 比如將襯片倒角，在制動鉗和制動襯塊之間加潤滑脂或者涂膠，在襯塊背板 上粘貼絕緣體（阻尼材料）等，可以減輕制動尖叫現(xiàn)象。很多時候，寒冷的 天氣加上清晨較大的濕度（露水）可能會夾具制動尖叫問題，尤其是當襯片 達到常規(guī)操作溫度時，甚至?xí)苿邮?。?/p>

8、而也有些襯片磨損指示器被設(shè)計 成當襯片需要更換時發(fā)出尖叫。整體看來，制動尖叫會給車輛內(nèi)的乘客、路 人、行人等帶來煩擾，尤其是對那些以更舒適安靜為設(shè)計目標的車輛。因此整車nvh （噪聲，振動，不平順性）性能是當今汽車制造商最重要 的考慮因素之一。制動器中的灰塵也可能引起制動尖叫。有許多商業(yè)制動器 清潔產(chǎn)品，可用來清除制動器中的灰塵和污染物。一些高性能制動襯塊，比 如鷹牌性能襯塊，在使用過程中會一直尖叫，但這并不表示有問題。除了制 動尖叫帶來的噪音之外，制動器也可能出現(xiàn)制動抖動或顫抖的現(xiàn)象。制動塵埃當施加制動力時，會逐漸地從制動襯塊上磨掉少許的材料。這些碎屑被 稱為“制動粉塵”，通常會沉積在制動系

9、統(tǒng)和周圍的車輪中。制動塵埃若不清 除，將會嚴重損害大多數(shù)輪胎的使用。不同的制動摩擦片配方會產(chǎn)生不同數(shù) 量的塵埃，有些配方相對于其他的更具破壞性。我們都知道踩下制動踏板會降低車速至停車，但這是怎么發(fā)生的呢？車 輛是如何將你退步的力量傳遞到車輪上的呢？它是如何將力放大到足以讓像 汽車那么大的物體停下來的呢？典型制動系統(tǒng)的布置當你踩下制動踏板，汽車通過液體將你腳下的力傳到制動器上。由于實 際上制動器需要的力比人的腿部可以提供的大得多，因而汽車必須放大你腳 上的力。有以下兩種方式：1機械優(yōu)勢（杠桿作用）2液力放大作用制動器靠摩擦力將力傳遞給車輪，同樣，車輪也是靠摩擦將力傳遞到路 面。在我們開始討論制動

10、系統(tǒng)的組成部分之前，我們將涵蓋以下三條原理：1杠桿作用2液壓3摩擦鼓式制動器和盤式制動器工作原理是一樣的：制動蹄壓緊在旋轉(zhuǎn)表面上。 在此系統(tǒng)中，這個表面被稱為制動鼓。許多汽車后輪采用鼓式制動器，前輪采用盤式制動器。鼓式制動器較盤 式的有更多零部件，而且制動效率更低，但它的制造成本較低，更容易安裝 應(yīng)急制動裝置。在部件如何運作這一版塊中，我們將清晰的了解到鼓式制動 系統(tǒng)如何運作的，檢查緊急制動的設(shè)置，并找出需要什么樣的行車制動器。 鼓式制動器可能看起來很復(fù)雜，當你打開一個的時候，可能會被嚇一跳。讓 我們把它拆解開來，并一一解釋每個部分。和盤式制動器一樣，這個鼓式制 動器有2個制動蹄，一個活塞輪缸

11、。但鼓式制動器還有個調(diào)整裝置，應(yīng)急制 動裝置和一些彈簧。當踩下制動踏板，活塞將制動蹄壓向制動鼓。當制動蹄 接觸到制動鼓上時，將會有一種楔入作用，它將起到使制動蹄以更大的力壓 向制動鼓的作用。楔入作用提供的額外制動力使得鼓式制動器可比盤式制動器使用更小的 活塞，然而，由于楔入作用，當釋放制動時，必須將制動蹄從制動鼓上拉離。 其中一些彈簧就是為了這個原因。其他的彈簧負責使制動蹄述有起作用后的 調(diào)整臂復(fù)位。制動器調(diào)整為使鼓式制動器正常工作，制動蹄必須和制動鼓保持接近，但又不接觸 上它。如果它們離制動鼓太遠（例如制動蹄磨損太多），活塞就需要更多的液 體來達到這個行程，當踩下剎車時，制動踏板將會更靠近地

12、板。這就是 為何 鼓式制動器需要自動調(diào)整裝置的原因。當制動襯片磨損時，制動蹄和鼓之間 將會形成很大間隙。每次停車的背后，都是制動蹄壓緊制動鼓。當間隙大到 一定程度，調(diào)整杠桿搖到足夠調(diào)整齒輪前進一個齒。調(diào)整器上有螺紋，就像 個螺栓，當它轉(zhuǎn)動時，使其旋開一點點，旋到填補產(chǎn)生的間隙。當制動蹄再 次磨損時，調(diào)整器繼續(xù)前進，因而它總是讓制動蹄靠近制動鼓。一些汽車的 調(diào)整裝置在施加應(yīng)急制動時被驅(qū)動。當應(yīng)急制動器長時間不用時，這種類型 的調(diào)整器也可單獨進行調(diào)整。要是你用的就是這種類型的調(diào)整器的話，你最 好至少每周用一次你的應(yīng)急制動器。維修對鼓式制動器最常需要的維修是更換制動蹄。一些鼓式制動器背面有個 觀察孔

13、。從那兒你可以看到制動蹄上還有多少材料。當摩擦材料磨損到釧釘 的1/32英寸（0.8毫米）時，制動蹄就應(yīng)該更換了。要是摩擦材料粘接到支承 底板上（無釧釘）時，當耐磨材料只剩下1/16英寸（1.6毫米）時，制動蹄就 該更換了。和盤式制動器一樣，深些的劃痕有時也會損壞制動鼓。如果產(chǎn)生磨損的 制動蹄仍被長時間使用的話，連接耐磨材料和襯背的釧釘會透過槽進入制動 鼓中。有劃傷的制動鼓有的可以通過返工修光處理被修復(fù)。鼓式制動器有個 最大允許直徑，而盤式制動器有個最小允許厚度。由于接觸表面是制動鼓的 內(nèi)表面，當鼓式制動器材料磨損時，直徑就會變大。盤式制動器的主要組成部分是：1剎車片2卡鉗，其中包含一個活塞3

14、轉(zhuǎn)子，安裝在輪轂上盤式制動器的部件盤式制動器和自行車上的制動器很像。自行車制動器有一個卡鉗，它壓 緊固聯(lián)車輪上的剎車片。在盤式制動器中，剎車片壓緊轉(zhuǎn)子而不是車輪，并 且力是通過液壓傳遞地而不是通過線纜。剎車片和制動盤之間的摩擦使得制 動盤減速。行駛中的汽車具有一定的動能，制動器要想使車輛停下就必須從車上移 除這些能量。制動器是如何做到這點的呢？毎次停車時，制動器都會將動能轉(zhuǎn)化成襯片和制動盤之間摩擦產(chǎn)生的熱能。大多數(shù)汽車盤式制動器是通風(fēng)盤 式。盤式制動器通風(fēng)孔通風(fēng)盤制動器在制動盤的兩側(cè)有一組葉片，將空氣泵過制動盤以提供冷 卻。自動調(diào)整制動器單活塞浮動鉗盤式制動器有自動定心和自動調(diào)整功能?？ㄣQ能夠

15、從一側(cè) 滑到另一側(cè)，以致每次施加制動時，他都將移動到中心處。另外，由于沒有 彈簧將襯片拉離制動盤，襯片始終和轉(zhuǎn)子保持輕微接觸（事實上，橡膠活塞 密封圈和轉(zhuǎn)子的任何搖晃都可能將襯片從轉(zhuǎn)子上拉離一小段距離）。這點很重 要，因為制動器中的活塞直徑比主缸活塞直徑大得多。如果活塞縮回制動器 主缸，它將可能需要多次踩下制動踏板，向制動輪缸泵入足夠的液體，以使 制動襯片壓緊。老式汽車有雙重或四個活塞固定卡鉗設(shè)計。轉(zhuǎn)子每一側(cè)有一 個活塞（或兩個）壓緊制動襯片。這種設(shè)計已經(jīng)基本淘汰，因為單缸活塞設(shè) 計更便宜也更可靠。應(yīng)急制動四輪全采用全盤式制動器的汽車中，應(yīng)急制動器必須由獨立的機械裝置 驅(qū)動，以防止主制動器失效

16、時，整個制動器都失效。大多數(shù)汽車用纜繩來驅(qū) 動應(yīng)急制動器。盤式制動器駐車制動有些四輪全盤式制動器的汽車，在后輪輪轂上有一個獨立的集成鼓式制 動器。這個鼓式制動器只用于應(yīng)急制動系統(tǒng)，僅由纜繩驅(qū)動；沒有液壓系統(tǒng) 參與。其他汽車有個杠桿轉(zhuǎn)動螺桿，或驅(qū)動一個凸輪，來壓緊盤式制動器中 的活塞。動力制動器是如何工作的如果你曾打開過汽車的引擎蓋，你可能已經(jīng)看到了制動助力器。它是個 圓的，黑色儲罐，安置在汽車發(fā)動機艙的后部，駕駛員的一側(cè)。早先，當大部分汽車還是鼓式制動器時，動力制動器還不是真的有必要。鼓式制動器本身就能夠起到一些助力作用?，F(xiàn)在因為大部分汽車都采用了盤 式制動器，至少前輪都是盤式的，他們就需耍動

17、力制動器。要不是有這種裝 置，許多駕駛員駕駛起來，腿部會很累。制動助力器利用發(fā)動機提供的真空 來放大你的腳施加在制動主缸上的力。真空助力器真空助力器是一個有著自動閥和隔膜的金屬罐。一根穿過小罐屮心的桿一側(cè)連著制 動缸活塞，一側(cè)連著制動踏板。動力制動器屮另一個重要的部件是單向閥。braking systemshow a brake system worksbrake systems were designed to slow the vehicles wheel movement through friction. today there are primarily two brake syst

18、ems, abs and none abs systems (anti brake skid) one system is basic hydraulics that work with a master brake cylinder (which is connected to the brake pedal in the car) that supplies brake fluid pressure to the front brake calipers and rear brake wheel cylinders or brake calipers if so equippeddrum

19、brakea drum brake is a brake in which the friction is caused by a set of shoes or pads that press against the inner surface of a rotating drum. the drum is connected to a rotating wheel.historythe modern automobile drum brake was invented in 1902 by louis renault, though a less sophisticated drum br

20、ake had been used by maybach a year earlier. in the first drum brakes, the shoes were mechanically operated with levers and rods or cables. from the mid-1930s the shoes were operated with oil pressure in a small wheel cylinder and pistons, though some vehicles continued with purely-mechanical system

21、s for decades. some designs have two wheel cylinders. the shoes in drum brakes are subject to wear and the brakes needed to be adjusted regularly until the 1950s introduction of selfadjusting drum brakes. in the 1960s and 1970s brake drums on the front wheels of cars were gradually replaced with dis

22、c brakes and now practically all cars use disc brakes on the front wheels, with many offering disc brakes on all wheels. however, drum brakes are still often used for handbrakes as it has proved very difficult to design a disc brake suitable for holding a car when it is not in use. moreover, it is v

23、ery easy to fit a drum handbrake inside a disc brake so that one unit serves for both foot brake and handbrake. early type brake shoes contained asbestos. when working on brake systems of older cars, care must be taken not to inhale any dust present in the brake assembly. the federal government bega

24、n to regulate asbestos production, and there was a period of time where owners complained of poor braking with the non-asbestos linings. eventually technology advanced to compensate. a majority of daily-driven older vehicles have been fitted with asbestos-free linings.servo designdrum brakes, depend

25、ing on the way the shoes are hinged, can have a ”self-servo” characteristic. this increases stopping power without any additional effort by the driver because the rotation of the drum drags the shoes around with it, increasing the force holding them together. in rear brakes only one shoe will have t

26、his characteristic. front drum brakes may use two actuating cylinders which allow both shoes to utilize the servo characteristic and which also increase the front axle braking force, required to compensate for forward weight shift and also to avoid premature rear wheel locking. servo action can be u

27、sed to make a very powerful brake (as on the rear axles of large commercial vehicles), but it does reduce the ability of the driver to modulate the brakes sensitively. (the disc brake has no self-servo effect because the pads act perpendicularly to the rotating disc.) advantagesdrum brakes are still

28、 used in modern cars. there can be engineering and cost advantages. drum brakes allow simple incorporation of a parking brake. they are often applied to the rear wheels since most of the stopping happens in the front of the vehicle and therefore the heat generated in the rear is significantly less.

29、drum brakes are also occasionally fitted as the parking (and emergency) brake even when the rear wheels used disk brakes as the main brakes. in this situation, a small drum is usually fitted within or as part of the brake disk.an advanced technology hybrid car using drum rear brakes is the toyota pr

30、ius. (4-wheel discs are used in certain markets - hybrid vehicles greatly reduce everyday wear on braking systems owing to their energy recovery motor-generators, see regenerative braking).disadvantagesdrum brakes with internal shoes have a particular disadvantage; when the drums are heated by hard

31、braking the diameter of the drum increases due to the expansion of the material and the brakes must be further depressed to obtain effective braking action. this is known as brake fade and can lead to driver panic and brake failure in extreme circumstances. under normal driving conditions it is seld

32、om noticed, especially when drums of appropriate size are fitted. the pontiac gto is one vehicle often cited as having undersized drums.brake padsthe brake pads are designed for high friction with brake pad material embedded in the disc in the process of bedding while wearing evenly. although it is

33、commonly thought that the pad material contacts the metal of the disc to stop the car, the pads work with a very thin layer of their own material and generate a semi-liquid friction boundary that creates the actual braking force. of course, depending on the properties of the material, disc wear coul

34、d be faster or slower than with other pads. the properties that determine material wear involve trade-offs between performance and longevity.the brake pads must be replaced regularly, and most are equipped with a method of alerting the driver when this needs to take place. some have a thin piece of

35、soft metal that causes the brakes to squeal when the pads are too thin, while others have a soft metal tab embedded in the pad material that closes an electric circuit and lights a warning light when the brake pad gets thin. more expensive cars may use an electronic sensor. although almost all road-

36、going vehicles have only two brake pads per caliper, racing calipers utilise up to six pads, with varying frictional properties in a staggered pattern for optimum performance. early brake pads (and shoes) contained asbestos. when working on an older car's brakes, care must be taken not to inhale

37、 any dust present on the caliper (or drum).brake squealsometimes a loud noise or high pitch squeal occurs when the brakes are applied. most brake squeal is produced due to vibration (resonance instability)of the brake components especially the pads and discs. this type of squeal does not negatively

38、affect brake stopping performance. some simple techniques like adding chamfers to linings, greasing or gluing the contact between caliper and the pads (finger to backplate, piston to backplate), bonding insulators (damping material) to pad backplate, etc might help reduce squeal. many times cold wea

39、ther combined with high early morning humidity (dew) could make the brake squeal worse and vanishes when the lining reaches regular operating temperatures. however, some lining wear indicators are also designed to squeal when the lining is due for replacement. overall brake squeal can be annoying to

40、 the vehicle passengers, passerby, pedestrians, etc especially as vehicles are designed to be more comfortable and quieter. hence vehicle nvh (noise, vibration and harshness) is one of the important priorities for today's vehicle manufacturers. an age-old trick is to put a small amount of copper

41、 slip (copper grease) onto the back of the pads where they contact the brake caliper piston and on the pad shims, if present. while this will normally stop the squeal, getting grease on the pads or disks will affect braking performance. dust on the brakes may also cause squeal; there are many commer

42、cial brake cleaning products that can be used to remove dust and contaminants from the brakes. some high-performance brake pads, such as hawk performance pads, will always squeal during operation, and this does not indicate a problem. apart from noise generated from squeal, brakes may also develop a

43、 phenomenon called brake judder or shudde匸brake dustwhen braking force is applied, small amounts of material are gradually ground off the brake pads. this material is known as hbrake dust11 and usually deposits itself on the braking system and the surrounding wheel. brake dust can badly damage the f

44、inish of most wheels if not washed off. different brake pad formulations create different amounts of dust, and some formulations are much more damaging than others.we all know that pushing down on the brake pedals lows a car to a stop. but how does this happen? how does your car transmit the force f

45、rom your leg to its wheels? how does it multiply the force so that it is enough to stop something as big as a car?layout of typical brake systemwhen you depress your brake pedal, your car transmits the force from your foot to its brakes through a fluid. since the actual brakes require a much greater

46、 force than you could apply with your leg, your car must also multiply the force of your foot. it does this in two ways:1 mechanical advantage(leverage)2 hydraulic force multiplicationthe brakes transmit the force to the tires using friction, and the tires transmit that force to the road using frict

47、ion also. before we begin our discussion on the components of the brake system, well cover these three principles:1 leverage2 hydraulics3 frictiondrum brakes work on the same principle as disc brakes: shoes press against a spinning surface. in this system, that surface is called a drum.many cars hav

48、e drum brakes on the rear wheels and disc brakes on the front. drum brakes have more parts than disc brakes and are harder to service, but they are less expensive to manufacture, and they easily incorporate an emergency brake mechanism. in this edition of how stuff works, we will learn exactly how a

49、 drum brake system works, examine the emergency brake setup and find out what kind of servicing drum brakes needthe drum brake may look complicated, and it can be pretty intimidating when you open one up lets break it down and explain what each piece does. like the disc brake, the drum brake has two

50、 brake shoes and a piston. but the drum brake also has an adjuster mechanism, an emergency brake mechanism and lots of springs. when you hit the brake pedal, the piston pushes the brake shoes against the drum. as the brake shoes contact the drum, there is a kind of wedging action, which has the effe

51、ct of pressing the shoes into the drum with more force. the extra braking force provided by the wedging action allows drum brakes to use a smaller piston than disc brakes. but, because of the wedging action the shoes must be pulled away from the drum when the brakes are released. this is the reason

52、for some of the springs. other springs help hold the brake shoes in place and return the adjuster arm after it actuates.brake adjusterfor the drum brakes to function correctly, the brake shoes must remain close to the drum without touching it. if they get too far away from the drum (as the shoes wea

53、r down, for instance), the piston will require more fluid to travel that distance, and your brake pedal will sink closer to the floor when you apply the brakes. this is why most drum brakes have an automatic adjuste匚 as the pad wears down, more space will form between the shoe and the drum. each tim

54、e the car stops while in reverse, the shoe is pulled tight against the drum. when the gap gets big enough, the adjusting lever rocks enough to advance the adj uster gear by one tooth. the adjuster has threads on it, like a bolt, so that it unscrews a little bit when it turns, lengthening to fill in

55、the gap. when the brake shoes wear a little more, the adjuster can advance again, so it always keeps the shoes close to the drum. some cars have an adjuster that is actuated when the emergency brake is applied. this type of adjuster can come out of adjustment if the emergency brake is not used for l

56、ong periods of time. so if you have this type of adjuster, you should apply your emergency brake at least once a week.servicingthe most common service required for drum brakes is changing the brake shoes. some drum brakes provide an inspection hole on the back side, where you can see how much materi

57、al is left on the shoe. brake shoes should be replaced when the friction material has worn down to within 1/32 inch (0.8 mm) of the rivets. if the friction material is bonded to the backing plate (no rivets), then the shoes should be replaced when they have only 1/16 inch (1.6 mm) of material left.

58、just as in disc brakes, deep scores sometimes get worn into brake drums. if a worn-out brake shoe is used for too long, the rivets that hold the friction material to the backing can wear grooves into the drum. a badly scored drum can sometimes be repaired by refinishing. where disc brakes have a min

59、imum allowable thickness, drum brakes have a maximum allowable diameter. since the contact surface is the inside of the drum, as you remove material from the drum brake the diameter gets bigger.the main components of a disc brake are:1 the brake pads2 the caliper, which contains a piston3 the rotor, which is mounted to the hubparts of a disc brakethe disc brake is a lot l