汽車車架設(shè)計(jì)

1、汽車設(shè)計(jì)-車架設(shè)計(jì)車架是汽車最根本的臺(tái)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(huì)使汽車既無法轉(zhuǎn)向，也無法進(jìn)行正常操縱。而如果汽車車架結(jié)構(gòu)剛性過大，乂會(huì)引起不必要的震動(dòng)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(jì)不僅決定了汽車噪聲大小和震動(dòng)的幅度強(qiáng)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?cè)谒麄兩a(chǎn)的汽車上都使用了幾種不同的車架結(jié)構(gòu)。其中，整個(gè)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(dòng)機(jī)、傳動(dòng)裝置、傳動(dòng)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)部的絕緣裝

2、置是人造橡膠緩沖墊，能夠阻止道路不平和發(fā)動(dòng)機(jī)工作引起的噪音和震動(dòng)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(jì)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(qiáng)度來分，設(shè)計(jì)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(qiáng)度。傳動(dòng)齒輪和傳動(dòng)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(dòng)和震動(dòng)。假設(shè)絕緣墊太軟，將會(huì)引起傳動(dòng)齒輪和傳動(dòng)裝置位移。這種位移稱為柔量，它會(huì)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(dòng)的作用。汽車制造廠商們精心地設(shè)計(jì)絕緣墊，把它們裝置在汽車適當(dāng)?shù)牡胤?，?/p>

3、降低噪聲，緩沖震動(dòng)的傳送，使汽車便丁駕駛，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(shí)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(diǎn)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(qiáng)了絕緣作用。汽車制造廠家們?cè)谄嚿线x擇那種生產(chǎn)本錢低而同時(shí)乂符合對(duì)噪音震動(dòng)，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(dòng)機(jī)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：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

4、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(rùn)滑不良的條件下工作?；钊苯优c高溫氣體接觸，瞬時(shí)溫度可達(dá)2500K以上，因此，受熱嚴(yán)重，而散熱條件乂很差，所以活塞工作時(shí)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(jī)高達(dá)35MPa,柴油機(jī)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(qiáng)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)運(yùn)動(dòng)，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

5、很大的附加載荷?；钊谶@種惡劣的條件下工作，會(huì)產(chǎn)生變形并加速磨損，還會(huì)產(chǎn)生附加載荷和熱應(yīng)力，同時(shí)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窃诰譁?、局壓、局速活塞平均速度可達(dá)101115m/s的條件下工作的，其潤(rùn)滑條件較差，活塞與氣缸壁問摩擦嚴(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(qiáng)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(qiáng)度鋁合金，但在一些低速柴油機(jī)上采用高級(jí)鑄鐵或耐熱鋼。構(gòu)造：活塞可分為三局部，活塞頂部、活塞頭部和活塞裙部?；钊?/p>

6、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(jiǎn)單平頂活塞頂部是一個(gè)平面，結(jié)構(gòu)簡(jiǎn)單，制造容易，受熱面積小，加工簡(jiǎn)單，頂部應(yīng)力分布較為均勻，一般用在汽油機(jī)上，柴油機(jī)很少采用。凸頂活塞多用丁二沖程內(nèi)燃機(jī)上，有利丁改善換氣過程?，F(xiàn)代四沖程汽油機(jī)為了增強(qiáng)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(qiáng)度高，起導(dǎo)向作用，有利丁改善換氣過程，二行程汽油機(jī)常采用凸頂活塞。凹頂活塞頂部呈凹陷形，凹坑的形狀和位置必須有利丁可燃混合氣的燃燒，有雙

7、渦流凹坑、球形凹坑、U形凹坑等等。活塞頭部指第一道活塞環(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，乂稱為防漏部。柴油機(jī)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(jī)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(jī)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，從而減輕第一道氣環(huán)的熱負(fù)荷。有的發(fā)動(dòng)機(jī)，在活塞頂面至第一道環(huán)槽之間，有時(shí)一直到以下幾道環(huán)槽處，常加工出細(xì)小的

8、環(huán)行槽。這種細(xì)小的環(huán)行槽可以因積碳而吸附潤(rùn)滑油，在失油工作時(shí)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钊^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(shí)還將（7080）%的熱量通過活塞環(huán)傳給氣缸壁。活塞裙部指從油環(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?duì)活塞在氣缸內(nèi)的往復(fù)運(yùn)動(dòng)起導(dǎo)向作用，并承受側(cè)壓力。裙部的長(zhǎng)短取決丁側(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

9、。壓縮行程和作功行程氣體的側(cè)壓力方向正好相反，由丁燃燒壓力大大高丁壓縮壓力，所以，作功行程中的側(cè)壓力也大大高丁壓縮行程中的側(cè)壓力?；钊共砍惺軅?cè)壓力的兩個(gè)側(cè)面稱為推力面，它們處丁與活塞銷軸線相垂直的方向上。動(dòng)力傳動(dòng)系統(tǒng)動(dòng)力傳動(dòng)系統(tǒng)包括從發(fā)動(dòng)機(jī)直到驅(qū)動(dòng)輪的所有部件。聯(lián)動(dòng)裝置和后驅(qū)動(dòng)裝置傳送著來自發(fā)動(dòng)機(jī)的扭矩。其它部件那么把部件與部件相互連接起來。加速時(shí)發(fā)動(dòng)機(jī)的扭矩和制動(dòng)時(shí)的扭矩那么加載在懸架部位上。修理懸架時(shí)，很可能需要拆卸傳動(dòng)系統(tǒng)的各零部件來進(jìn)行修理。懸架移動(dòng)時(shí)產(chǎn)生的噪音可能來源丁傳動(dòng)系統(tǒng)的零部件。下邊表達(dá)一些不同的傳動(dòng)裝置系統(tǒng)的根本知識(shí)，在進(jìn)行懸架修理時(shí)可供參考。使用前輪驅(qū)動(dòng)的傳動(dòng)系統(tǒng)經(jīng)常將

10、聯(lián)動(dòng)裝置和后輪傳動(dòng)裝置結(jié)合成一個(gè)裝置。這個(gè)對(duì)中置和后置發(fā)動(dòng)機(jī)的汽車也是很適用的。這個(gè)裝置稱為轉(zhuǎn)換軸。它為兩端各帶有一個(gè)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(dòng)和轉(zhuǎn)向時(shí)把動(dòng)力從后傳動(dòng)裝置傳送到車輪上。后傳動(dòng)裝置里的差速器分流輸入的動(dòng)力，每個(gè)驅(qū)動(dòng)輪上各分一半。這就使驅(qū)動(dòng)輪在轉(zhuǎn)彎時(shí)會(huì)以不同的速度轉(zhuǎn)動(dòng)。在前置發(fā)動(dòng)機(jī)后輪驅(qū)動(dòng)的汽車?yán)?，?lián)動(dòng)裝置位丁駕駛坐艙的前底板下。傳動(dòng)軸被用來把發(fā)動(dòng)機(jī)動(dòng)力傳送到后橋上。傳動(dòng)軸每端各有一個(gè)萬向節(jié)。當(dāng)懸架移動(dòng)時(shí)，萬向節(jié)通過變化著的傳動(dòng)系統(tǒng)的角度傳送動(dòng)力。驅(qū)動(dòng)輪上帶有獨(dú)立懸架的汽車中有一個(gè)牢固地附加在車身大梁或發(fā)動(dòng)機(jī)上的后傳動(dòng)裝置。在加速時(shí)該裝置在懸架部位上會(huì)

11、產(chǎn)生動(dòng)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(huì)在懸架上產(chǎn)生扭矩。僅用丁控制加速和減速扭矩的懸架與必須同時(shí)控制懸架力和扭矩的懸架在汽車設(shè)計(jì)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(dòng)機(jī)和制動(dòng)對(duì)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(shí)間盡可能的長(zhǎng)。在支撐車體和負(fù)載時(shí)，甚至在上下不平的道路上行駛時(shí)更加應(yīng)如此。這四個(gè)輪胎的胎面是車與路面相接觸的唯一的部位。發(fā)動(dòng)機(jī)全部輸出的動(dòng)力，轉(zhuǎn)向力和制動(dòng)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(shí)，

12、汽車的控制力動(dòng)力、轉(zhuǎn)向力、制動(dòng)力就會(huì)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(duì)車體的橫向和縱向控制，以防止汽車車輪在行駛時(shí)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(yùn)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(jì)目的是截然不同的?，F(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

13、。要想要最大限度的平安駕車，要牢記這四個(gè)輪胎必須在任何時(shí)間都與路面相接觸。同時(shí)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(jì)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(qiáng)度、支撐型獨(dú)立懸架結(jié)構(gòu)，并由丁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進(jìn)行改良的。大多數(shù)前置發(fā)動(dòng)機(jī)，后輪驅(qū)動(dòng)的汽車都采用一個(gè)簡(jiǎn)單的附屆性后懸架。但后輪驅(qū)動(dòng)的獨(dú)立懸架結(jié)構(gòu)復(fù)雜得多，而且本錢極高，因而只用丁少數(shù)客車上。對(duì)丁前置發(fā)動(dòng)機(jī)前輪驅(qū)動(dòng)的車輛，通過把傳動(dòng)裝置移至前部，后懸架僅用

14、來調(diào)節(jié)駕駛控制力和剎車時(shí)的反作用。這就導(dǎo)致了簡(jiǎn)化的非獨(dú)立的懸架機(jī)構(gòu)，半獨(dú)立的懸架機(jī)構(gòu)和獨(dú)立的后懸架機(jī)構(gòu)的應(yīng)用，后者大量應(yīng)用丁新型車輛的結(jié)構(gòu)設(shè)計(jì)上。轉(zhuǎn)向系統(tǒng)汽車駕駛員通過對(duì)轉(zhuǎn)向齒輪的控制汽車前輪的方向?，F(xiàn)代的轉(zhuǎn)向齒輪有兩個(gè)主要的局部組成，轉(zhuǎn)向桿和齒輪組。轉(zhuǎn)向桿有一個(gè)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(dòng)轉(zhuǎn)向連桿裝置。后輪驅(qū)動(dòng)汽車的前輪在一個(gè)心軸上轉(zhuǎn)動(dòng)。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(dòng)時(shí)可以進(jìn)行轉(zhuǎn)向。前輪驅(qū)動(dòng)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(dòng)。汽車方向盤控制轉(zhuǎn)向齒輪裝置。它依次通

15、過轉(zhuǎn)向連桿裝置使轉(zhuǎn)向節(jié)開始移動(dòng)?，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(jì)了對(duì)速度敏感的轉(zhuǎn)向結(jié)構(gòu)。因此當(dāng)汽車慢速行駛時(shí)需要較大的力才能使汽車轉(zhuǎn)向。丁是在很多汽車上裝備了助力轉(zhuǎn)向裝置。由丁助力轉(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(dòng)方向盤使得汽車轉(zhuǎn)向。助力轉(zhuǎn)向齒輪類似丁標(biāo)準(zhǔn)的轉(zhuǎn)向齒輪。它有承壓面，液體壓力加在其上，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(dòng)力輔助裝置。轉(zhuǎn)向齒輪的動(dòng)力是由發(fā)動(dòng)機(jī)從動(dòng)泵提供的。該泵使動(dòng)力轉(zhuǎn)向液體流過一個(gè)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

16、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(gè)部件組成。它被用來分散、抵消汽車碰撞力以保護(hù)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(shí)機(jī)，還安裝有一個(gè)轉(zhuǎn)向齒輪的保險(xiǎn)鎖。很多汽車還有一個(gè)變速器保險(xiǎn)鎖。因?yàn)樘幵隈{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器換擋控制滑桿，轉(zhuǎn)向信號(hào)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(dòng)系使用中的制動(dòng)器應(yīng)能起到制動(dòng)住車輛的作用。制動(dòng)器能使汽車滑行時(shí)能防止行駛速度過快，在斜坡上制動(dòng)時(shí)能將汽車停在適當(dāng)?shù)奈恢蒙?。汽車剎車的設(shè)計(jì)應(yīng)使駕駛員能調(diào)節(jié)制動(dòng)力以控制汽車

17、。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(dòng)系統(tǒng)的故障可導(dǎo)致汽車剎車時(shí)車輪滑脫。要修理懸梁系統(tǒng)，也可能需要將制動(dòng)系統(tǒng)的部件拆卸開。為此本文將討論制動(dòng)系統(tǒng)。制動(dòng)系統(tǒng)應(yīng)給予汽車駕駛員提供均勻平穩(wěn)的制動(dòng)力。剎車板上所需的力不應(yīng)太大，而使車輪不至丁被瞬間剎死。為滿足這些汽車剎車的要求，對(duì)丁汽車制動(dòng)已有了最低限度的剎車標(biāo)準(zhǔn)。駕駛員通過機(jī)械裝置、真空和液壓裝置控制制動(dòng)力。制動(dòng)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(gè)力通過制動(dòng)系統(tǒng)的傳遞以把固定的汽車剎車片推壓到轉(zhuǎn)動(dòng)的制動(dòng)器外表上。當(dāng)它把動(dòng)能運(yùn)動(dòng)的能量轉(zhuǎn)化為熱能熱時(shí)，就使汽車減速。制動(dòng)量的最大值就產(chǎn)生丁車輪被瞬間閘死而引起的

18、輪胎在路面上滑動(dòng)之前。所以制動(dòng)量的最大值取決丁輪胎和路面之間的附著力。當(dāng)輪胎在道路上滑動(dòng)時(shí)，制動(dòng)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(dòng)。汽車的制動(dòng)盤剎車時(shí)：汽車制動(dòng)盤剎車有隨車輪一起轉(zhuǎn)動(dòng)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(huì)減慢或阻止車輪的轉(zhuǎn)動(dòng)。固定的卡鉗殼體使墊圈被壓在轉(zhuǎn)動(dòng)的汽車剎車盤上，使之不能轉(zhuǎn)動(dòng)。汽車制動(dòng)盤剎車墊圈的運(yùn)動(dòng)與剎車轉(zhuǎn)子的外表垂直，這樣會(huì)使它們卡在轉(zhuǎn)子

19、上減慢汽車的車輪運(yùn)動(dòng)?？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(dòng)鼓剎車：汽車制動(dòng)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(dòng)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(shí)，汽車剎車塊就減慢了汽車剎車鼓的轉(zhuǎn)動(dòng)。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(jī)械連桿進(jìn)行移動(dòng)，把汽車剎車片壓到轉(zhuǎn)動(dòng)的剎車鼓上。當(dāng)汽車剎車鼓的轉(zhuǎn)動(dòng)速度減慢時(shí)，就起到了制動(dòng)作用。AutomobileDesign-FrameDesign

20、sThevehicleframeisthebasicplatformtowhichallsuspensionandsteeringlinkagepartsattach.Avehiclewillneithersteernorhandlewelliftheframeistooflexible.Arigidframestructuremaypassunnecessaryvibrationsintothepassengercompartment.Theframeandsuspensiondesignwillaffecttheridequality,handling,anddurability,aswe

21、llasthelevelsofbothnoiseandvibration.Manufacturersuseseveraldifferenttypesofconstructionontheirvehicles.Ofthese,separatebodyandframeconstructionwasthemostcommonthroughthe1970's.Itisstillusedinlargevans,pickups,andtrucks.Inthistypeofconstruction,theengine,driveline,runninggear,andbodymounttothefr

22、amethroughinsulators.Insulatorsaresyntheticrubberpadsthatkeeproadandenginenoiseandvibrationfromgoingintothepassengercompartment.Asecondtypeofconstructionistheunitizedbody.This,designisbyfarthemostpopularinmodernvehicles.Theunitizeddesignhasalightweightstructurewiththerequiredstrength.Tnthistypeofcon

23、struction,theframeisweldedintothebodyaspartofthebodystructure.Bodypanelsaddstrengthtotheframepieces.Therunninggearanddrivelinearemountedtotheunitizedbodythroughlarge,softsyntheticrubberinsulators.Theinsulatorsminimizethetransferofnoiseandvibration.Iftheinsulatorsaretoosoft,theywillallowtoomuchrunnin

24、ggearanddrivelinemovement.Thismovement,calledcompliance,affectsvehiclehandlingandcontrol.Iftheinsulatorsaretoohard,theywillnotinsulatenoiseandvibrationastheyshould.Themanufacturercarefullydesignstheinsulatorsandputsthemwheretheywillbeinavehiclewithlownoiseandvibrationtransmissionthatstillhasproperha

25、ndlingandfeel.Insulatorpropertieschangewithage,changingoriginalcharacteristicsasthevehiclebecomesolder.Athirdtypeofconstructioncombinesthefeaturesofthefirstandsecondtypes.Itusesastubframefromthebulkheadforwardandaunitizedbodyfromthebulkheadback.Theunitizedpartisveryrigid,whilethestubframeprovidesapl

26、aceforgoodinsulation.Manufacturersselectthetypeofconstruction.thatismosteconomicaltobuild,'whileprovidingthenoise,vibration,andrideandhandlingcharacteristicstheywantinthevehicle.Largeoldervehicles,vans,andtrucksgenerallyuseseparatebodyandframeconstruction.Thenewer,smaller'vehiclesgenerallyus

27、eunitizedconstruction.ThemachinepistonconnectingrodsetThepistonconnectingrodsetiscomposedofthepiston,pistonwreath,pistonpin,connectingrod,connectingrodaxlebush,etc.effect:Theeffectofthepistonistobeartheairpressure,andpasstoconnectingrodtodrivethebentaxletorevolvethroughconnectingrodaxlebush,thepisto

28、ncopingisstillapartoftheburningroom.Theworkcondition:Pistonworksundertheconditionofheat,highpressure,highspeed,andbadlubrication.Pistondirectlycontactswiththeheatair.Thetemperaturecanamounttoabove2500Ksinamoment.Thepistonisheatedseverely,buttheconditionofspreadingthehotisbad.Sowhilethepistonworks,th

29、etemperatureisveryhighandthecopingisuptothe600-700Ks:Andthetemperaturedistributesasymmetrically;Thepistoncopingbearsgreatairpressure,especiallythepressureisgreatestintherouteofdoingefficacy.Thegasolinemachineisuptothe3-5MPas,thedieselengineisuptothe6-9MPas.Thismakesthepistonproducepound,andbearthefu

30、nctionofthesidepressure.Therefore,thepistonshouldhaveenoughheat-proof,trytodecreasetheheatingarea,strengthenthecoolingofthepiston,tomakethehighesttemperatureofthecopingdescend.Thepistonmovesatveryhighspeed(8-12ms/s)backandforthintheaircylinder,andspeedchangesconstantly,Thisproducesverygreatinertiald

31、int,makingthepistonbeargreatadditionalloadworkingundersuchbadcondition,thepistonwillbecomedeformedheatingpower.Atthesametime,itslittersthechemicalcorrosivepoweroftheburninggas.Inordertodescendtheinertialdintofbackandforth,wemusteasetheweightofthepistonaspossible.Pistonworksundertheconditionoftheheat

32、,highpressure,highspeed(theaveragespeedcanamounttothe101115m/s),anditslubricantconditionisbadandthefricationbetweenthepistonandtheaircylinderwallisverygreat.Inordertodescendthefriction,thesurfaceofthepistonsurfacemustbewear-resistant.Request:1) Tohaveenoughrigidityandstrength,andthereliabledint;2) T

33、ransmitheatwell,bearthehighpressure,beartheheatandbeartowearaway;3) thequantityissmall,theweightislight,descendtheinertialdintofbackandforthaspossibleThealuminummetalalloymaterialsatisfiesthetoprequestsbasically,therefore,thepistongenerallyadoptsthehighstrengthaluminummetalalloy,butsomelowspeeddiese

34、lenginesadopthighclassironcastingorheat-proofsteelstructure:Thepistoncanbedividedintothreeparts,pistoncoping,thepistonheadandpistonskirtdepartments.1. ThepistoncopingThepistoncopingbearstheairpressure,itisapartoftheburnableroom.Itsshape,position,sizearerelevanttotheconcretefromoftheburnableroom.They

35、aremadetosatisfythecombustiblehybridspiritformationandburnablerequests.Itscopingshapecanbedividedintofourmajortypes,aflatcopingpiston,aconvexcopingpiston,aconcavecopingpistonandmodelpiston.AconvexcopingpistonisusuallyusedonthetwobluntdistanceI.C.engines,Itisgoodtoimprovetheprocessexchangingthegas.Mo

36、dernfourbluntthedistancegasolinemachinealsoadoptstheconvexcopingpistoninordertostrengthentheeffectofpushingthegasorextendtheratioofcompressing.Convexofapistoncopingpresentsaformofball,itscopingstrengthishigh,havinganeffectofleading,beingadvantageoustoimprovetheprocessofexchangingthegas,tworouteoftra

37、velgasolinemachinesoftenadopttheconvexcopingpistonApistoncopingpresentsthehollowform,theshapeandpositionsofthecavepitmustbeadvantageoustothecombustionofthecombustibleandhybridgas,havingapairofeddiesconcavepitball,concavepit,Uconcavepit,andsoon.2. PistonheadThepistonreferstothefirstpistonwreathtothep

38、artabovethepistonpin.Ithasseveralwreathslots,whichareusedtoinstallthepistonwreathandhaveaneffectofsealingcompletely.Itisalsocalledtheleakproofdepartment.Thedieselengine'scompressratioishigh,andgenerallyhavefourwreathslots,Thethreeupperwreathsareusedtoinstall,thelowerpartinstallstheoilwreath.Theg

39、asolinemachinehasthreewreathslotsgenerally,whicharetwojetofgaswreathslotsandanoilwreathslots.Atthebottomofoilwreathslotmanypathstowardeyeletaredrilledtomakethequiltoilwreathflowfromtheaircylinderwalltotheoilbottomhullthroughtheseeyelets.Theworkingconditionofthewreathslotistheworstandshouldleavetheco

40、pinggenerallyalittlefarther.Abovethegaswreath,anarrowinsulatingslotisusuallysettocutofftheheatflowwhichisspreadfromthepistoncopingtothefirstgaswreathandmakepartsofcaloriesfromapistonwreathspread,thuseasingthehotburdenofthefirstgaswreath.Onsomeenginessmallwreatheslotsareoftenmadebetweenthecopingheada

41、ndthefirstgaswreathe,sometimestillafewmorewreath.Thiskindofsmallwreathcanadsorbthelubricantbecauseitaccumulatesthecarbon.Itcankeeppistonandtheaircylinderwallsfrombitingtomatchwhenitworkintheconditionoflosingoil,soitiscalledaccumulatingthecarbonslot.Thecaloriesthatthepistoncopingabsorbsalsomainlypass

42、estheaircylinderwallthroughthepistonwreathtoleakproofdepartment,againspreadbythecoolwater.Inaword,thefunctionofthepistonheadisinadditiontoinstallthepistonwreath,stillsealcompletelyfunctionandtransmitheatfunction,sealingcompletelytheaircylindertogetherwiththepistonwreath,keepingcombustibleadmixturesp

43、iritfromleakcrankcase,atthesametimepassthe(70-80)%caloriestotheaircylinderwallthroughthepistonwreath.3. PistonskirtdepartmentThepistonskirtdepartmentreferstothepartsfromthebottomoftheoilwreatheslot.Itincludesthepinwhichisusedtopackthepiston.Thepistonskirtdepartmentexercisestorisetoleadtothefunctiont

44、othepistoninthebackandforthintheaircylinder,andbearthesidepressure.Thelengthoftheskirtdepartmentisdecidedbythesizeandthepistondiameterofthesidepressure.Theso-calledsidepressuremeaninthecompressionrouteoftravelandmakerouteoftravelofefficacy.Thelevelcomponentofthegaspressurewhichtakeeffectonthepistonc

45、opingpressesthepistontotheaircylinderwall.Compresstherouteoftravelandmakethesidepressuredirectionoftheefficacyrouteoftravelairexactlytheopposite,becauseofthecombustionpressureconsumedlyhighincompressthepressure,so,makethesideintherouteoftravelofefficacypressurealsoconsumedlyhighincompressthesideinth

46、erouteoftravelpressure.Twoonthesidesthatbearthesidepressureofthepistonskirtdepartmentbecalledtopushthedinttoface,theybeplacedintosellthemutuallyperpendiculardirectionofthestalklinewithpistonup.DriveLinesThedrivelineincludesallthepartsfromtheandfinaldrivecarrythetorquefromtheengine,theother.Theengine

47、torqueduringaccelerationandthetorqueduringbrakingplaceloadsonthesuspensionparts.Duringsuspensionrepair,itmaybeessarytodisassemblepartsofthedriveline.Noisesproducedwhenthesuspensionmovesmayoriginatefromdrivelineparts.Abasicunderstandingofdifferentdrivelineassembliesispresentedheretogiveyouaworkingkno

48、wledgesothatyoucandosuspensionrepair.Drivelineswithfront-wheeldriveoftencombinethetransmissionandthefinaldriveintooneassembly.Thisisalsotrueofmid-andrear-enginevehicles.Theassemblyiscalledatransaxle,Shorthalf-shaftswithuniversaljointsateachendconnectbetweenthetransaxleandthewheels.Theseshaftscarrypo

49、werfromthefinaldrivetothewheelsevenwhenthesuspensionmovesandsteers.Adifferentialinthefinaldrivesplitsincomingpower,sendinghalftoeachdrivewheel.Thisallowsthedrivewheelstoturnatdifferentspeedswhileroundingcorners.ThetransmissionOtherpartsformthelinkfromoneparttowhilecornering.Infront-engine,rear-wheel

50、drivevehicles,thetransmissionislocatedunderthefrontfloorofthepassengercompartment.Adriveshaftisusedtocarryenginepowertotherearaxle.Thedriveshafthasauniversaljointateachend.Itcarriespowerthroughthechangingdrivelineanglesasthesuspensionmoves.Avehiclewithindependentsuspensionatthedrivewheelshasthefinal

51、driveattachedrigidlytothevehicleframeortheengine.Thisdrivearrangementproducesforces,withoutanytorques,onthesuspensionpartsduringacceleration.Ifthebrakesaremountedinboardsothecalipermountstoaframepieceandnottoasuspension,thebrakewillalsonotproduceatorqueonthesuspension.Asuspensiondesignedtohandleonly

52、accelerationandbrakingtorquescanbedesigneddifferentlythanonethatmusthandlebothsuspensionforcesandtorques.SuspensionSystemsThesuspensionincludessprings,shockabsorbers,andcontrollinkages.Itmustbestrongenoughtosupportthevehiclebodyandload.Thesuspensionmustalsoresistengineandbrakereactions.Themostimport

53、antjobofthesuspensionistokeepthetiresincontactwiththeroadasmuchofthetimeaspossible.Thisisdonewhilesupportingthevehicleanditsload,evenwhiletravelingoverroughroads.Thefourtirefootprintsaretheonlyplacethevehicletouchestheroad.Alloftheenginepower,steering,andbrakingforcesoperatethroughthetire-to-roadfoo

54、tprints.Controlofthevehicle(power,steeringandbraking)isreducedorlostanytimeatiredoesnotstayontheroadorwhenskiddingbegins.Thevehiclebodyissupportedbysprings.Thespringscanbeofthecoil,leaf,torsionbar,orpneumatictype.Coilspringsarethemostpopulardesignusedinthemodernautomobile.Coil,torsionbar,andpneumati

55、cspringsallrequirelinksandarmstoholdthewheelinposition.Leafspringsprovidelateralandlongitudinalcontroltopreventunwantedwheelmotions.Theyarecommonlyfoundonvansandtrucks.Suspensionsystemshavebeenchangedandrefinedasthepassengerautomobilehasdeveloped.Designobjectivesdifferbetweenluxurysedans,performance

56、vehicles,smallcompactvehicles,andlighttrucks.Tireimprovements,alongwithimprovementsinshockabsorbers,steeringsystems,andsuspensioncontroldevices,havecontinuallyupgradedvehiclehandlingcharacteristics.Tire-to-roadcontactisneededforsafe,positivevehiclecontrolunderalloperatingconditions.Keepinmindthatall

57、fourtiresmuststayincontactwiththeroadatalltimesformaximumvehiclecontrol.Compromisesaremadeinhandlingresponse,tirewear,drivercomfort,andrideharshnesstoachievepositivevehiclecontrol.Suspensionsystemsaredividedintofrontsuspensionandrearsuspension.Frontsuspensiondesignshavedevelopedfromrelativelyruggeds

58、olid-axledesignstothemodernlightweight,high-strength,strut-typeindependentdesigns.Thesehavebeenupgradedwithaddedlinkage.Suspensiondesignimprovementshavefollowedimprovementsinroadwaysanddriverexpectations.Mostfront-engine,rear-wheel-drivevehiclesuseasimpledependentrearsuspension.Rear-wheel-driveindep

59、endentsuspensionismuchmorecomplexandexpensive.Asaresult,itisonlyusedonafewpassengervehicles.Tofront-engine,front-wheel-drivevehiclesbymovingthedrivetraintothefront,onlyridecontrolandbrakingreactionsarecontrolledbytherearsuspension.Thishasledtotheuseofsimplifieddependentsuspension,semi-independentsuspensionandindependentrearsuspension.Thelatterisusedinalargernumberofnewvehicledesigns.SteeringSystemsThedrivercontrolst