汽車車架設(shè)計

1、汽車設(shè)計-車架設(shè)計車架是汽車最根本的臺架，所有的懸架和轉(zhuǎn)向連接部件都安裝在車架上面。 如果汽車車架柔性過大，會使汽車既無法轉(zhuǎn)向，也無法進行正常操縱。而如果汽 車車架結(jié)構(gòu)剛性過大，又會引起不必要的震動傳遞給駕駛員和乘客的座艙室。汽 車車架和懸架的結(jié)構(gòu)設(shè)計不僅決定了汽車噪聲大小和震動的幅度強度，而且也將影響到汽車的質(zhì)量和車輛的正常操縱。汽車制造廠商們在他們生產(chǎn)的汽車上都使用了幾種不同的車架結(jié)構(gòu)。其中， 整個七十年代最常使用的是殼體和大梁的分體結(jié)構(gòu)。目前它仍然在大型貨車、小噸位貨車和卡車上應(yīng)用著。在汽車殼體和大梁的分體結(jié)構(gòu)里，發(fā)動機、傳動裝置、 傳動齒輪和車殼都是通過絕緣裝置固定在車身大梁上。車架內(nèi)

2、部的絕緣裝置是人 造橡膠緩沖墊，能夠阻止道路不平和發(fā)動機工作引起的噪音和震動傳到駕駛員和 乘客的座艙里。第二種是汽車車架的單體結(jié)構(gòu)。這種設(shè)計到目前為止在現(xiàn)代汽車上是最常 用。單體車架按所需的強度來分，設(shè)計有輕型結(jié)構(gòu)。在這種汽車結(jié)構(gòu)中大梁作為 車架的一局部被直接焊接到殼體上。 底盤的重量增加了大梁的強度。傳動齒輪和 傳動裝置經(jīng)由大而軟的人造橡膠絕緣墊安裝在單體車架上。絕緣墊減弱了噪聲的傳動和震動。假設(shè)絕緣墊太軟，將會引起傳動齒輪和傳動裝置位移。 這種位移稱 為柔量，它會影響到汽車的操縱性能和控制性能。 假設(shè)絕緣墊太硬，那么不能起 到應(yīng)有的隔絕噪音和減小震動的作用。汽車制造廠商們精心地設(shè)計絕緣墊，

3、把它 們裝置在汽車適當(dāng)?shù)牡胤?，以降低噪聲，緩沖震動的傳送，使汽車便于駕駛，駕 駛員和乘客乘坐舒適。絕緣墊的性能隨使用年限發(fā)生變化，當(dāng)汽車變舊時原先的 性能也隨之改變。第三種結(jié)構(gòu)是把前兩種結(jié)構(gòu)的主要特點結(jié)合在一起。 它在汽車前艙使用了短 車梁，在汽車后艙使用了單體車架。 單體局部剛性很大，而短的車梁增強了絕緣 作用。汽車制造廠家們在汽車上選擇那種生產(chǎn)本錢低而同時又符合對噪音震動， 駕 駛操縱性能要求很高的車架結(jié)構(gòu)。老式的大型的車輛、貨車、和卡車通常使用殼 體和大梁的分體結(jié)構(gòu)。較新的，較小型的車輛通常使用單體結(jié)構(gòu)的車架。發(fā)動機活塞連桿組活塞連桿組由活塞、活塞環(huán)、活塞銷、連桿、連桿軸瓦等組成。功用：

4、活塞的功用是承受氣體壓力，并通過活塞銷傳給連桿驅(qū)使曲軸旋轉(zhuǎn)， 活塞頂部還是燃燒室的組成局部。工作條件：活塞在高溫、高壓、高速、潤滑不良的條件下工作?；钊苯优c高溫氣體接觸，瞬時溫度可達(dá)2500K以上，因此，受熱嚴(yán)重，而散熱條件又很差，所以活塞工作時溫度很高，頂部高達(dá)600700K，且溫度分布很不均勻；活塞頂部承受氣體壓力很大，特別是作功行程壓 力最大，汽油機高達(dá)35MPa,柴油機高達(dá)69MPa，這就使得活塞產(chǎn)生沖擊， 并承受側(cè)壓力的作用，因此，活塞應(yīng)有足夠的耐熱性，要盡量減小活塞的受熱面， 加強活塞的冷卻，適當(dāng)增大傳熱面，使活塞頂部的最高溫度下降?；钊跉飧變?nèi) 以很高的速度（812m/s）往復(fù)

5、運動，且速度在不斷地變化，這就產(chǎn)生了很大的慣 性力，使活塞受到很大的附加載荷?；钊谶@種惡劣的條件下工作，會產(chǎn)生變形 并加速磨損，還會產(chǎn)生附加載荷和熱應(yīng)力，同時受到燃?xì)獾幕瘜W(xué)腐蝕作用。為了減小往復(fù)慣性力，必須盡可能地減輕活塞的重量?；钊窃趩J溫、咼壓、咼速活塞平均速度可達(dá)101115m/s的條件下工作的，其潤滑條件較差，活塞與氣 缸壁間摩擦嚴(yán)重。為減小摩擦，活塞外表必須耐磨。要求：1）要有足夠的剛度和強度，傳力可靠；2）導(dǎo)熱性好，耐高壓、耐高溫、耐磨損；3）質(zhì)量小，重量輕，盡可能減小往復(fù)慣性力。鋁合金材料根本上滿足上面的要求，因此，活塞一般都采用高強度鋁合金， 但在一些低速柴油機上采用高級鑄鐵

6、或耐熱鋼。構(gòu)造：活塞可分為三局部，活塞頂部、活塞頭部和活塞裙部。活塞頂部承受氣體壓力，它是燃燒室的組成局部，其形狀、位置、大小都和 燃燒室的具體形式有關(guān)，都是為滿足可燃混合氣形成和燃燒的要求， 其頂部形狀 可分為四大類，平頂活塞、凸頂活塞、凹頂活塞和成型頂活塞。加工簡單平頂活塞頂部是一個平面，結(jié)構(gòu)簡單，制造容易，受熱面積小，加 工簡單，頂部應(yīng)力分布較為均勻，一般用在汽油機上，柴油機很少采用。凸頂活塞多用于二沖程內(nèi)燃機上，有利于改善換氣過程?，F(xiàn)代四沖程汽油機 為了增強擠氣效果或增大壓縮比也有采用凸頂活塞。凸頂活塞頂部凸起呈球頂 形，其頂部強度高，起導(dǎo)向作用，有利于改善換氣過程，二行程汽油機常采用

7、凸 頂活塞。凹頂活塞頂部呈凹陷形，凹坑的形狀和位置必須有利于可燃混合氣的燃燒， 有雙渦流凹坑、球形凹坑、U形凹坑等等?；钊^部指第一道活塞環(huán)槽到活塞銷孔以上局部。它有數(shù)道環(huán)槽，用以安裝活塞環(huán)，起密封作用，又稱為防漏部。柴油機壓縮比高，一般有四道環(huán)槽，上部 三道安裝氣環(huán)，下部安裝油環(huán)。汽油機一般有三道環(huán)槽，其中有兩道氣環(huán)槽和一 道油環(huán)槽，在油環(huán)槽底面上鉆有許多徑向小孔，使被油環(huán)從氣缸壁上刮下的機油 經(jīng)過這些小孔流回油底殼。第一道環(huán)槽工作條件最惡劣，一般應(yīng)離頂部較遠(yuǎn)些。在一道氣環(huán)的上方往往開有一道較窄的隔熱槽， 隔斷由活塞頂部傳向第一道 氣環(huán)的熱流，使局部熱量由第二、三道活塞環(huán)傳出，從而減輕第一道

8、氣環(huán)的熱負(fù) 荷。有的發(fā)動機，在活塞頂面至第一道環(huán)槽之間，有時一直到以下幾道環(huán)槽處， 常加工出細(xì)小的環(huán)行槽。這種細(xì)小的環(huán)行槽可以因積碳而吸附潤滑油， 在失油工 作時可防止活塞與氣缸壁的咬合，故稱之為積碳槽。活塞頂部吸收的熱量主要也是經(jīng)過防漏部通過活塞環(huán)傳給氣缸壁， 再由冷卻 水傳出去?？傊?，活塞頭部的作用除了用來安裝活塞環(huán)外， 還有密封作用和傳熱 作用，與活塞環(huán)一起密封氣缸，防止可燃混合氣漏到曲軸箱內(nèi)，同時還將 （70 80）%的熱量通過活塞環(huán)傳給氣缸壁?；钊共恐笍挠铜h(huán)槽下端面起至活塞最下端的局部，它包括裝活塞銷的銷座孔?；钊共繉钊跉飧變?nèi)的往復(fù)運動起導(dǎo)向作用，并承受側(cè)壓力。裙部的長短取決

9、于側(cè)壓力的大小和活塞直徑。所謂側(cè)壓力是指在壓縮行程和作功行程中， 作用在活塞頂部的氣體壓力的水平分力使活塞壓向氣缸壁。壓縮行程和作功行程氣體的側(cè)壓力方向正好相反，由于燃燒壓力大大高于壓縮壓力， 所以，作功行程 中的側(cè)壓力也大大高于壓縮行程中的側(cè)壓力。 活塞裙部承受側(cè)壓力的兩個側(cè)面稱 為推力面，它們處于與活塞銷軸線相垂直的方向上。動力傳動系統(tǒng)動力傳動系統(tǒng)包括從發(fā)動機直到驅(qū)動輪的所有部件。聯(lián)動裝置和后驅(qū)動裝置 傳送著來自發(fā)動機的扭矩。其它部件那么把部件與部件相互連接起來。加速時發(fā) 動機的扭矩和制動時的扭矩那么加載在懸架部位上。修理懸架時，很可能需要拆卸傳動系統(tǒng)的各零部件來進行修理。懸架移動時 產(chǎn)生

10、的噪音可能來源于傳動系統(tǒng)的零部件。 下邊表達(dá)一些不同的傳動裝置系統(tǒng)的 根本知識，在進行懸架修理時可供參考。使用前輪驅(qū)動的傳動系統(tǒng)經(jīng)常將聯(lián)動裝置和后輪傳動裝置結(jié)合成一個裝置。 這個對中置和后置發(fā)動機的汽車也是很適用的。 這個裝置稱為轉(zhuǎn)換軸。它為兩端 各帶有一個萬向節(jié)的短半軸，把轉(zhuǎn)換軸和車輪連接起來。這些軸當(dāng)懸梁移動和轉(zhuǎn) 向時把動力從后傳動裝置傳送到車輪上。后傳動裝置里的差速器分流輸入的動力， 每個驅(qū)動輪上各分一半。這就使驅(qū) 動輪在轉(zhuǎn)彎時會以不同的速度轉(zhuǎn)動。在前置發(fā)動機后輪驅(qū)動的汽車?yán)铮?lián)動裝置位于駕駛坐艙的前底板下。傳動 軸被用來把發(fā)動機動力傳送到后橋上。傳動軸每端各有一個萬向節(jié)。當(dāng)懸架移動 時

11、，萬向節(jié)通過變化著的傳動系統(tǒng)的角度傳送動力。驅(qū)動輪上帶有獨立懸架的汽車中有一個牢固地附加在車身大梁或發(fā)動機上 的后傳動裝置。在加速時該裝置在懸架部位上會產(chǎn)生動力，并不產(chǎn)生扭矩。如果 剎車裝置安裝在車艙內(nèi)，卡鉗裝到大梁上而不是懸架上，那么剎車裝置也不會在 懸架上產(chǎn)生扭矩。僅用于控制加速和減速扭矩的懸架與必須同時控制懸架力和扭 矩的懸架在汽車設(shè)計上是完全不相同的。懸架系統(tǒng)懸架包括彈簧，避震器和控制連桿裝置。它必須能夠足以支撐車身自重和負(fù) 載。懸架也應(yīng)能夠承受發(fā)動機和制動對它的反作用力。懸架系統(tǒng)最重要的作用是 使輪胎與路面接觸的時間盡可能的長。 在支撐車體和負(fù)載時，甚至在上下不平的 道路上行駛時更加

12、應(yīng)如此。這四個輪胎的胎面是車與路面相接觸的唯一的部位。 發(fā)動機全部輸出的動力，轉(zhuǎn)向力和制動力都通過與路面相接觸的輪胎的胎面起作 用。每當(dāng)輪胎不與路面接觸或汽車開始打滑時，汽車的控制力動力、轉(zhuǎn)向力、 制動力就會減弱甚至喪失。車體是靠彈簧支撐著，彈簧可分為螺旋型、鋼板型、扭棒型和充氣型。螺旋 型彈簧是現(xiàn)代汽車中應(yīng)用最為廣泛的類型。 螺旋型、扭棒型和充氣型彈簧都需要 用連桿和連桿臂以使車輪就位。鋼板彈簧提供了對車體的橫向和縱向控制， 以防 止汽車車輪在行駛時不必要的位移，它們通常用在載重貨車和卡車上。懸架系統(tǒng)是隨著客運汽車的開展而變化和改良著。 豪華轎車，特種車輛，小 型汽車和輕型卡車的設(shè)計目的是截

13、然不同的。 現(xiàn)代輪胎的改良不斷地改善了車輛 的操作性能，它的改良是與避震器，轉(zhuǎn)向系統(tǒng)和懸架控制裝置一起同步改良的?，F(xiàn)代汽車在各種操縱條件下都需要輪胎與路面接觸，以便平安、正確地控制 并行駛汽車。要想要最大限度的平安駕車，要牢記這四個輪胎必須在任何時間都 與路面相接觸。同時需要考慮汽車操縱的靈活性，輪胎的抗耐磨性，汽車駕駛的 舒適性和行車的平安性，以到達(dá)汽車的有效控制。懸架系統(tǒng)分為前懸架和后懸架。前懸架的設(shè)計已得到了飛速開展。 從較為粗 糙的硬軸結(jié)構(gòu)開展到了現(xiàn)代的輕型、 高強度、支撐型獨立懸架結(jié)構(gòu)，并由于增加 了連桿裝置而使汽車的性能得到了改善。 懸架結(jié)構(gòu)的改良是隨著路況的改善和駕 駛員的需要而

14、進行改良的。大多數(shù)前置發(fā)動機，后輪驅(qū)動的汽車都采用一個簡單的附屬性后懸架。但后輪驅(qū)動的獨立懸架結(jié)構(gòu)復(fù)雜得多，而且本錢極高，因而只用于少數(shù)客車上。對于前置發(fā)動機前輪驅(qū)動的車輛，通過把傳動裝置移至前部，后懸架僅用來 調(diào)節(jié)駕駛控制力和剎車時的反作用。 這就導(dǎo)致了簡化的非獨立的懸架機構(gòu)， 半獨 立的懸架機構(gòu)和獨立的后懸架機構(gòu)的應(yīng)用，后者大量應(yīng)用于新型車輛的結(jié)構(gòu)設(shè)計 上。轉(zhuǎn)向系統(tǒng)汽車駕駛員通過對轉(zhuǎn)向齒輪的控制汽車前輪的方向。 現(xiàn)代的轉(zhuǎn)向齒輪有兩個 主要的局部組成，轉(zhuǎn)向桿和齒輪組。轉(zhuǎn)向桿有一個被支撐的軸，它把駕駛員的方 向盤與齒輪組連在了一起。齒輪組可將汽車駕駛員的轉(zhuǎn)向力增大， 以帶動轉(zhuǎn)向連 桿裝置。后輪

15、驅(qū)動汽車的前輪在一個心軸上轉(zhuǎn)動。 心軸是轉(zhuǎn)向節(jié)的一局部。該轉(zhuǎn)向節(jié) 與帶有球接頭的前懸橫梁相互連接。球接頭在前懸架上下移動時可以進行轉(zhuǎn)向。 前輪驅(qū)動的汽車的輪轂在轉(zhuǎn)向節(jié)里的軸承內(nèi)的空心軸短軸桿上傳動。汽車方向盤控制轉(zhuǎn)向齒輪裝置。它依次通過轉(zhuǎn)向連桿裝置使轉(zhuǎn)向節(jié)開始移 動?，F(xiàn)在使用兩種轉(zhuǎn)向齒輪的結(jié)構(gòu)，即齒輪齒條式結(jié)構(gòu)以及循環(huán)球式結(jié)構(gòu)?，F(xiàn)代汽車設(shè)計了對速度敏感的轉(zhuǎn)向結(jié)構(gòu)。因此當(dāng)汽車慢速行駛時需要較大的 力才能使汽車轉(zhuǎn)向。于是在很多汽車上裝備了助力轉(zhuǎn)向裝置。由于助力轉(zhuǎn)向裝置起了主要作用，所以轉(zhuǎn)向比降低了，這樣就能夠輕微轉(zhuǎn)動 方向盤使得汽車轉(zhuǎn)向。助力轉(zhuǎn)向齒輪類似于標(biāo)準(zhǔn)的轉(zhuǎn)向齒輪。 它有承壓面，液體 壓力加

16、在其上，以增加汽車駕駛員的轉(zhuǎn)向力。齒輪齒條式轉(zhuǎn)向結(jié)構(gòu)和循環(huán)球齒輪 結(jié)構(gòu)都有了動力輔助裝置。轉(zhuǎn)向齒輪的動力是由發(fā)動機從動泵提供的。 該泵使動力轉(zhuǎn)向液體流過一個由 閥體控制的系統(tǒng)。該控制閥能感知汽車駕駛員的轉(zhuǎn)向力。把液體壓力加到轉(zhuǎn)向系 統(tǒng)的承壓面上。該液體壓力承接了一些使汽車轉(zhuǎn)向的力?，F(xiàn)在汽車的轉(zhuǎn)向桿有很多個部件組成。它被用來分散、抵消汽車碰撞力以保 護駕駛員的切身平安。在有些汽車上轉(zhuǎn)向桿還可以傾斜和伸縮來調(diào)節(jié)方向盤的位 置使駕駛員感覺更加舒適。為了減少駕駛員汽車被盜的時機，還安裝有一個轉(zhuǎn)向 齒輪的保險鎖。很多汽車還有一個變速器保險鎖。因為處在駕駛員很容易觸及的 范圍內(nèi)，所以轉(zhuǎn)向桿上還可以帶有變速

17、器換擋控制滑桿，轉(zhuǎn)向信號開關(guān)，前大燈 和變光開關(guān)，刮水器開關(guān)，緊急閃爍器開關(guān)和速度控制器。制動系使用中的制動器應(yīng)能起到制動住車輛的作用。 制動器能使汽車滑行時能防止 行駛速度過快，在斜坡上制動時能將汽車停在適當(dāng)?shù)奈恢蒙稀?汽車剎車的設(shè)計應(yīng) 使駕駛員能調(diào)節(jié)制動力以控制汽車。 汽車的控制不僅受懸架和轉(zhuǎn)向系統(tǒng)影響， 而 且也受汽車剎車影響。制動系統(tǒng)的故障可導(dǎo)致汽車剎車時車輪滑脫。要修理懸梁 系統(tǒng)，也可能需要將制動系統(tǒng)的部件拆卸開。為此本文將討論制動系統(tǒng)。制動系統(tǒng)應(yīng)給予汽車駕駛員提供均勻平穩(wěn)的制動力。 剎車板上所需的力不應(yīng) 太大，而使車輪不至于被瞬間剎死。為滿足這些汽車剎車的要求，對于汽車制動 已有了

18、最低限度的剎車標(biāo)準(zhǔn)。駕駛員通過機械裝置、真空和液壓裝置控制制動力。制動力是隨著附加在汽 車剎車板上的踏板力的增加而增加的。這個力通過制動系統(tǒng)的傳遞以把固定的汽 車剎車片推壓到轉(zhuǎn)動的制動器外表上。當(dāng)它把動能運動的能量轉(zhuǎn)化為熱能熱 時，就使汽車減速。制動量的最大值就產(chǎn)生于車輪被瞬間閘死而引起的輪胎在路 面上滑動之前。所以制動量的最大值取決于輪胎和路面之間的附著力。 當(dāng)輪胎在 道路上滑動時，制動效果減弱，汽車的方向控制可能就不起作用了。前剎車總成的固定構(gòu)件安裝在前懸架的轉(zhuǎn)向節(jié)上， 在后部，它們被安裝在后 橋殼或后心軸總成上，鑄鐵剎車鼓或車盤隨車輪一起轉(zhuǎn)動。汽車的制動盤剎車時：汽車制動盤剎車有隨車輪一

19、起轉(zhuǎn)動的圓盤。它通常被 稱為汽車剎車轉(zhuǎn)子。在固定的卡鉗里的液壓控制的活塞被用來把汽車的剎車片加 在轉(zhuǎn)子的汽車剎車外表上。汽車剎車片和轉(zhuǎn)子之間的摩擦力的大小會減慢或阻止 車輪的轉(zhuǎn)動。固定的卡鉗殼體使墊圈被壓在轉(zhuǎn)動的汽車剎車盤上，使之不能轉(zhuǎn)動。汽車制動盤剎車墊圈的運動與剎車轉(zhuǎn)子的外表垂直，這樣會使它們卡在轉(zhuǎn)子 上減慢汽車的車輪運動?？ㄣQ壓的力與駕駛員加在汽車剎車板上的力成正比。汽車制動鼓剎車：汽車制動鼓剎車使用帶有摩擦片的固定的內(nèi)脹式剎車塊。 他們被安裝在轉(zhuǎn)動的汽車剎車鼓內(nèi)側(cè)。汽車剎車鼓緊箍在輪胎總成和轂總成或輪 軸法蘭之間。當(dāng)汽車剎車塊的直徑膨脹至使汽車剎車片與汽車剎車外表相接觸 時，汽車剎車塊

20、就減慢了汽車剎車鼓的轉(zhuǎn)動。它是由液壓操縱的汽車剎車分泵來 完成的。來自剎車總泵的流體壓力被施加到汽車剎車分泵上，使剎車分泵膨脹起來。汽車剎車分泵的膨脹使剎車塊通過機械連桿進行移動，把汽車剎車片壓到轉(zhuǎn) 動的剎車鼓上。當(dāng)汽車剎車鼓的轉(zhuǎn)動速度減慢時，就起到了制動作用。Automobile Design-Frame DesignsThe vehicle frame is the basic platform to which all suspe nsion and steeri ng lin kage parts attach. A vehicle will n either steer nor ha

21、n dle well if the frame is too flexible. A rigid frame structure may pass unn ecessary vibrati ons into the passe nger compartme nt. The frame and suspe nsion desig n will affect the ride quality, han dli ng, and durability, as well as the levels of both no ise and vibrati on.Manu facturers use seve

22、ral differe nt types of con structi on on their vehicles. Of these, separate body and frame con struct ion was the most com mon through the 1970s. It is still used in large vans, pickups, and trucks. In this type of construction, the engine, drive line, running gear, and body mount to the frame thro

23、ugh in sulators. In sulators are syn thetic rubber pads that keep road and engine no ise and vibratio n from going into the passe nger compartme nt.A sec ond type of con struct ion is the un itized body. This, desig n is by far the most popular in modern vehicles. The unitized design has a lightweig

24、ht structure with the required stre ngth. Tn this type of con struct ion, the frame is welded into the body as part of the body structure. Body pan els add stre ngth to the frame pieces. The running gear and drive line are mounted to the unitized body through large, soft synthetic rubber insulators.

25、 The insulators minimize the transfer of noise and vibration. If the insulators are too soft, they will allow too much running gear and drive line moveme nt. This moveme nt, called complia nee, affects vehicle han dli ng and con trol. If the insulators are too hard, they will not insulate noise and

26、vibration as they should. The manu facturer carefully desig ns the in sulators and puts them where they will be in a vehicle with low no ise and vibrati on tran smissi on that still has proper han dli ng and feel. Insulator properties change with age, changing original characteristics as the vehicle

27、 becomes older.A third type of con structi on comb ines the features of the first and sec ond types. It uses a stub frame from the bulkhead forward and a unitized body from the bulkhead back. The un itized part is very rigid, while the stub frame provides a place for good in sulati on.Manufacturers

28、select the type of construction .that is most economical to build, while providing the noise, vibration, and ride and handling characteristics they want in the vehicle. Large older vehicles, vans, and trucks gen erally use separate body and frame con structi on. The n ewer, smaller vehicles gen eral

29、ly use un itized con structi on.The mach ine pist on conn ect ing rod setThe pist on connecting rod set is composed of the pist on, pist on wreath, pist on pin, conn ect ing rod, connecting rod axle bush, etc.effect: The effect of the pist on is to bear the air pressure, and pass to conn ect ing rod

30、 to drive the bent axle to revolve through connecting rod axle bush, the pist on coping is still a part of the burning room. The work condition: Piston works under the condition of heat, high pressure, high speed, and bad lubrication .Piston directly con tacts with the heat air. The temperature can

31、amount to above 2500 Ks in a moment .The piston is heated severely, but the condition of spreading the hot is bad .So while the pist on works, the temperature is very high and the cop ing is up to the 600-700 Ks: And the temperature distributes asymmetrically; The pisto n cop ing bears great air pre

32、ssure, especially the pressure is greatest in the route of doing efficacy. The gasoline machine is up to the 3-5MPas, the diesel engine is up to the 6-9MPas.This makes the pist on produce pound, and bear the fun cti on of the side pressure. Therefore, the pisto n should have eno ugh heat-proof, try

33、to decreasethe heating area, strengthen the cooling of the piston, to make the highest temperature of the cop ing desce nd .The pist on moves at very high speed(8-12 ms/ s) back and forth in the air cylinder, and speed changesconstantly, This produces very great inertial dint, making the pist on bea

34、r great additi on al load work ing un der such bad con diti on, the piston will become deformed heating power. At the same time ,it slitters the chemical corrosive power of the bur ning gasn order to desce nd the in ertial dint of back and forth, we must ease the weight of the piston as possible .Pi

35、ston works under the con diti on of the heat, high pressure, high speed(the average speed can amount to the 101115 m/ s), and its lubricant condition is bad and the frication between the piston and the air cylinder wall is very great. In order to descend the friction, the surface of the pisto n surf

36、ace must be wear-resista nt.Request:To have eno ugh rigidity and stre ngth, and the reliable dint;Transmit heat well, bear the high pressure, bear the heat and bear to wear away;the quantity is small, the weight is light, descend the inertial dint of back and forth as possibleThe aluminum metal allo

37、y material satisfies the top requests basically, therefore, the pisto n gen erally adopts the high stre ngth alumi num metal alloy, but some low speed diesel engines adopt high class iron casti ng or heat-proof steelstructure: The pist on can be divided into three parts, pist on cop ing, the pist on

38、 head and pist on skirt departme nts.The pist on cop ingThe piston cop ing bears the air pressure, it is a part of the burn able room .Its shape, positi on, size are releva nt to the con crete from of the bur nable room. They are made to satisfy the combustible hybrid spirit formation and burnable r

39、equests. Its coping shape can be divided into four major types, a flat coping piston, a convex cop ing pist on, a con cave cop ing pist on and model pist on.A con vex cop ing pist on is usually used on the two blunt dista nee I.C. engin es, It is good to improve the process exchanging the gas .Moder

40、n four blunt the distanee gasoline machine also adopts the convex coping piston in order to strengthen the effect of pushing the gas or extend the ratio of compressing .Convex of a piston cop ing prese nts a form of ball, its cop ing stre ngth is high, hav ing an effect of lead ing, being adva ntage

41、ous to improve the process of excha nging the gas, two route of travel gasoli ne machi nes ofte n adopt the convex cop ing pist onA pist on cop ing prese nts the hollow form, the shape and positi ons of the cave pit must be advantageous to the combustion of the combustible and hybrid gas, having a p

42、air of eddies con cave pit ball, con cave pit, U con cave pit, and so on.Piston headThe pist on refers to the first pist on wreath to the part above the pist on pin.lt has several wreath slots, which are used to in stall the pisto n wreath and have an effect of sealing completely. It is also called

43、the leak proof department .The diesel engine s compress ratio is high, and gen erally have four wreath slots, The three upper wreaths are used to in stall, the lower part in stalls the oil wreath. The gasoli ne mach ine has three wreath slots gen erally, which are two jet of gas wreath slots and an

44、oil wreath slots. At the bottom of oil wreath slot many paths toward eyelet are drilled to make the quilt oil wreath flow from the air cylinder wall to the oil bottom hull through these eyelets. The work ing con diti on of the wreath slot is the worst and should leave the cop ing gen erally a little

45、 farther.Above the gas wreath, a n arrow in sulat ing slot is usually set to cut off the heat flow which is spread from the pist on cop ing to the first gas wreath and make parts of calories from a pist on wreath spread, thus eas ing the hot burde n of the first gas wreath. On some engines small wre

46、athe slots are often made between the coping head and the first gas wreathe, sometimes till a few more wreath. This kind of small wreath can adsorb the lubrica nt because it accumulates the carb on. It can keep piston and the air cylinder walls from biting to match when it work in the condition of l

47、osing oil, so it is called accumulat ing the carb on slot.The calories that the piston coping absorbs also mainly passesthe air cylinder wall through the piston wreath to leak proof department, again spread by the cool water.In a word, the fun ctio n of the pisto n head is in additi on to in stall t

48、he piston wreath, still seal completely function and transmit heat function, sealing completely the air cylinder together with the piston wreath, keeping combustible admixture spirit from leak cran kcase,at the same time pass the(70-80)%calories to the air cyli nder wall through the pist on wreath.P

49、isto n skirt departme ntThe pist on skirt departme nt refers to the parts from the bottom of the oil wreathe slot. It in cludes the pin which is used to pack the pist on. The pist on skirt departme nt exercises to rise to lead to the function to the piston in the back and forth in the air cyli nder,

50、 and bear the side pressure. The len gth of the skirt departme nt is decided by the size and the pist on diameter of the side pressure. The so-called side pressure mean in the compression route of travel and make route of travel of efficacy .The level comp onent of the gas pressure which take effect

51、 on the pist on cop ing pressesthe piston to the air cylinder wall. Compress the route of travel and make the side pressure direct ion of the efficacy route of travel air exactly the opposite, because of the combusti on pressure con sumedly high in compress the pressure, so, make the side in the rou

52、te of travel of efficacy pressure also con sumedly high in compress the side in the route of travel pressure.Two on the sides that bear the side pressure of the pist on skirt departme nt be called to push the dint to face, they be placed in to sell the mutually perpe ndicular directi on of the stalk

53、 line with pisto n up.Drive LinesThe drive line includes all the parts from the and final drive carry the torque from the engine, the other. The engine torque duri ng accelerati on and the torqueduri ng brak ing place loads on the suspe nsion parts.During suspe nsion repair, it may be essary to disa

54、ssemble parts of the drive line. Noises produced whe n the suspe nsion moves may orig in ate from drive line parts. A basic un dersta nding of differe nt drive line assemblies is prese nted here to give you a work ing kno wledge so that you can do suspe nsion repair.Drive lines with front-wheel driv

55、e often combine the transmission and the final drive into one assembly. This is also true of mid-and rear-engine vehicles. The assembly is called a transaxle, Short half-shafts with universal joints at each end connect betwee n the tran saxle and the wheels. These shafts carry power from the final d

56、rive to the wheels eve n whe n the suspe nsion moves and steers.A differential in the final drive splits incoming power, sending half to each drive wheel. This allows the drive wheels to tur n at differe nt speeds while rounding corn ers. The transmission Other parts form the link from one part to w

57、hile cornering.In front-engine, rear-wheel drive vehicles, the transmission is located under the front floor of the passe nger compartme nt. A drive shaft is used to carry engine power to the rear axle. The drive shaft has a universal joint at each end. It carries power through the cha nging drive l

58、ine an gles as the suspe nsion moves.A vehicle with independent suspension at the drive wheels has the final drive attached rigidly to the vehicle frame or the engine. This drive arran geme nt produces forces, without any torques, on the suspension parts during acceleration. If the brakes are moun t

59、ed in board so the caliper moun ts to a frame piece and not to a suspe nsion, the brake will also not produce a torque on the suspe nsion. A suspe nsion desig ned to han dle only accelerati on and brak ing torques can be desig ned differe ntly tha n one that must han dle both suspe nsion forces and

60、torques.Suspe nsion SystemsThe suspe nsion in cludes spri ngs, shock absorbers, and con trol li nkages. It must be strong eno ugh to support the vehicle body and load. The suspe nsion must also resist engine and brake react ions. The most importa nt job of the suspe nsion is to keep the tires in con