盤式重型飛機(jī)牽引車的結(jié)構(gòu)設(shè)計

購買設(shè)計請充值后下載，資源目錄下的文件所見即所得，都可以點開預(yù)覽，資料完整，充值下載可得到資源目錄里的所有文件?！咀ⅰ浚篸wg后綴為CAD圖紙，doc,docx為WORD文檔，原稿無水印，可編輯。具體請見文件預(yù)覽，有不明白之處，可咨詢QQ:12401814 南京理工大學(xué)泰州科技學(xué)院 畢業(yè)設(shè)計(論文)外文資料翻譯 系 部： 機(jī)械工程 專 業(yè)： 機(jī)械工程及自動化 姓 名： 吳煒 學(xué) 號： 05010140 外文出處： https:/shop.sae.org 附 件： 1.外文資料翻譯譯文；2.外文原 文。 指導(dǎo)教師評語： 簽名： (用外文寫) 年 月 日 注：請將該封面與附件裝訂成冊。 附件 1：外文資料翻譯譯文 黏性連接器用作前輪驅(qū)動時限制滑移對汽車牽引和操縱的影 響 1 基本概念 黏性連接器主要地被認(rèn)為是在四輪驅(qū)動的汽車上驅(qū)動路線的部件。然而在近 些年的發(fā)展中，在主流的前輪驅(qū)動設(shè)備中這種裝置將成為主要角色，這個觀點是 有可能的。在歐洲和日本前輪驅(qū)動轎車產(chǎn)量的施用已經(jīng)證明黏性連接器不僅對于 光滑路面的汽車牽引，而且在正常行駛條件下對于操縱性和穩(wěn)定性都有所改善。 這篇文章展現(xiàn)了一系列地面測試試驗，顯示黏性連接器對前輪驅(qū)動汽車牽引 和操縱的影響。試驗證明僅有輕微轉(zhuǎn)向扭轉(zhuǎn)的時候，牽引力才會改善。前輪驅(qū)動 的汽車在直線行駛時，影響發(fā)動機(jī)轉(zhuǎn)矩的因素被確定出來。確定關(guān)鍵汽車設(shè)計參 數(shù)，對前輪驅(qū)動的汽車的限制滑移差速器適合性有極大地影響。 轉(zhuǎn)彎試驗展現(xiàn)出黏性連接器在前輪驅(qū)動的汽車上獨(dú)立轉(zhuǎn)彎時的影響。進(jìn)一步 的試驗證明安裝黏性限制滑移差速器的汽車在加速和轉(zhuǎn)彎時節(jié)氣門頻繁關(guān)閉的情 況下顯示出一個理想的穩(wěn)定性。 2 黏性連接器 黏性連接器被廣泛認(rèn)為是驅(qū)動列車的組成部件。在這篇文章中僅僅給出它的 基本功能和原理的簡明概要。 黏性連接器是根據(jù)液體摩擦的原理和依靠速度差來運(yùn)轉(zhuǎn)的。正如圖 1 所示黏 性連接器的滑動控制特性和驅(qū)動觀察系統(tǒng)的對比。 這表明傳送到前輪的驅(qū)動扭轉(zhuǎn)力是由一個優(yōu)化的扭轉(zhuǎn)力分配檢測器自動控制 的。 在前輪驅(qū)動的汽車上黏性連接器可以安裝在差速器的內(nèi)側(cè)或者一根中間軸的 外面。 內(nèi)部的這種設(shè)計方式有很大的優(yōu)點。首先，在中間軸區(qū)域可以得到足夠的空 間來提供符合要求的黏性特性。這和當(dāng)今前輪軸差速器只留下有限的空間相對比。 其次，差速器架和轉(zhuǎn)送軸套只需要很小的修改。而且差速器殼體的生產(chǎn)也僅僅只 有一點影響。引用作為一個選擇性的事很容易做到尤其當(dāng)軸和黏性單元作為一個 整體單元被共給時。最后，中間軸使為等長的的側(cè)偏軸提供橫向安裝發(fā)動機(jī)是可 能的，橫向地安裝發(fā)動機(jī)對于減小扭轉(zhuǎn)力的操縱是很重要的（后面第四部分說明 了） 。 這種特殊的設(shè)計也為有實際意義的重量和黏性單元費(fèi)用的降低給出了很好的 可能性。GKN Viscodrive 正在發(fā)展一種低重量和低成本的黏性連接器。通過使用 僅僅兩個標(biāo)準(zhǔn)化的直徑、標(biāo)準(zhǔn)化的盤，塑料輪轂和擠壓成型的材料造成的儲存室 它能很容易地被截成不同的長度，使用一個寬的黏性范圍是可能的。在圖 3 中顯 示出這種發(fā)展的一個例子。 3 牽引力的影響 作為一個扭轉(zhuǎn)力平衡裝置，一個開的差速器提供相等的力到兩個驅(qū)動輪上。 它也允許每個車輪在扭轉(zhuǎn)沒結(jié)束轉(zhuǎn)彎時以不同的速度轉(zhuǎn)動。然而，這種特性當(dāng)?shù)?路表面滑動系數(shù)為 限制扭轉(zhuǎn)力傳遞到兩輪的左、右附著變動時是不利的，它能 被低滑動系數(shù) 的輪子支持。 安裝黏性限制滑移差速器,在高的 值的路面上它可能利用高車輪潛在性的附 著。例如，當(dāng)一個車輪傳遞的最大扭轉(zhuǎn)力超出表面滑動系數(shù) 允許值或者以一個 高的側(cè)面加速度轉(zhuǎn)彎時，兩個車輪的速度是不同的.在黏性連接器中產(chǎn)生的自鎖扭 轉(zhuǎn)力抵抗速度差的增加并且傳遞合適的扭轉(zhuǎn)力到車輪上它具有更好的牽引力潛能。 可以看出牽引力的不同導(dǎo)致汽車瞬間向低滑動系數(shù)值( )一側(cè)跑偏，為了保 持汽車直線行駛駕駛員必須施加一個相反的扭轉(zhuǎn)力來補(bǔ)償。通過黏性連接器的液 體摩擦原理和從打開到鎖死柔和的傳遞結(jié)果,這是很可能的。 報告稱平均操縱輪扭轉(zhuǎn)力 和為保持帶有一個開式的并且黏性的差速器在加ST 速期間在滑動系數(shù) 的路面上直線行駛應(yīng)輸入的平均正確的相對的轉(zhuǎn)向操縱。相 互對照開式差速器和那些黏性連接器是相對大的。然而，在絕對條件下它們是小 的。主觀地說，轉(zhuǎn)向裝置的影響是不明顯的。扭轉(zhuǎn)力操縱也受幾個運(yùn)動參數(shù)影響 這些參數(shù)將在這篇文章下個部分解釋。 4 影響轉(zhuǎn)向裝置扭轉(zhuǎn)力的因素 牽引力引起一個從頭到尾的增加來反應(yīng)每個車輪。因為帶有限制滑動差速器 的車輪在滑動系數(shù) 的路面上加速時會出現(xiàn)不同的牽引力，所以從頭到尾反應(yīng)每 個車輪的變化也是不同的。 不幸的是，這個作用將導(dǎo)致一個不期望的朝低滑動系數(shù)一側(cè)的反應(yīng)，也就是 說在不同的牽引力下產(chǎn)生相同的跑偏方向。 降低從頭到尾的彈力是黏性限制滑動差速器像其它任何形式差速器一樣在前 軸的成功應(yīng)用所必須具備的。 普遍地用下面的公式計算一個車輪的驅(qū)動力 TVF 牽引力 車輪垂直載荷V 利用的附著系數(shù) 這些驅(qū)動力導(dǎo)致在車輪之間每個車輪的轉(zhuǎn)向裝置扭轉(zhuǎn)力經(jīng)過車輪干擾常數(shù) e 干擾后與每個車輪的轉(zhuǎn)向裝置扭轉(zhuǎn)力是不同的，給出下面的等式。 cos()ioeHhlTF 這里 扭轉(zhuǎn)力矩差值 e車輪干擾常數(shù) 主銷傾角 高滑動系數(shù)一側(cè)下標(biāo)ih 低滑動系數(shù)一側(cè)下標(biāo)ol 在帶有開式差速器前輪驅(qū)動汽車的情況下， 是很不明顯的，因為扭轉(zhuǎn)力基ST 數(shù) 是不大于 1.35 的。(/)HhiloF 然而，因為應(yīng)用了限制滑動差速器，這個影響是很有意義的。這樣車輪干擾常 數(shù) e 就應(yīng)該盡可能的小。不同的車輪載荷也會導(dǎo)致 的增加所以差別也要盡eTA 可能的小。 當(dāng)扭轉(zhuǎn)力通過鉸接“CV 連接”傳遞時，在主動一側(cè)（下標(biāo) 1）和從動一側(cè)（下 標(biāo) 2） ，必須反應(yīng)垂直平面相對于連接平面的不同的第二個力矩產(chǎn)生了。第二個力 矩（M）大小和方向用于下面的式子計算： 主動一側(cè) 12tan(/)/tanvvTTA 從動一側(cè) 2TdynFr(,f連 接 系 統(tǒng) ） 這里 縱向連接角v 產(chǎn)生的連接角 產(chǎn)生變化的輪子半徑dynr 平均扭轉(zhuǎn)力矩?fù)p失T 當(dāng)每個裝置的轉(zhuǎn)向扭轉(zhuǎn)力以及輪子之間的轉(zhuǎn)向裝置扭轉(zhuǎn)力不同時， 將圍繞著主銷軸線變動，如下所示：2cosMAT2 2(tan/sin)(tan/tan)vvwhivvwliTT 這里 轉(zhuǎn)向裝置扭轉(zhuǎn)力矩差 W輪子一側(cè)的下標(biāo) 因此很明顯不僅不同的驅(qū)動扭轉(zhuǎn)力而且黏性驅(qū)動軸長度的不同也是一個因素。 說道圖 7 中的力矩多邊形， 的旋轉(zhuǎn)方向或者 各自地變化，都取決于輪子中心2MT 到變速箱輸出的位置。 如圖 7 所示由于半軸的正常位置（輪子中心低于變速箱的輸出點）第二個力 矩產(chǎn)生和驅(qū)動力一樣的旋轉(zhuǎn)方向。由于改進(jìn)的懸掛裝置設(shè)計（車輪中心高于變速 箱輸出點，也就是說， 為負(fù)值）第二個力矩抵消了由驅(qū)動力引起的力矩。這樣v 為了得到帶一個限制滑動差速器前軸好的適應(yīng)性，設(shè)計要求：1）縱向彎曲角近似 或者負(fù)值（ ）且左側(cè)和右側(cè)的 值相等；2）等長度的側(cè)軸。0v0vv 第二力矩在轉(zhuǎn)向裝置的影響不僅僅是上面描述的限制直接反應(yīng)。從連接軸到 車輪側(cè)面和變速箱側(cè)面之間的連接點間接反應(yīng)也會產(chǎn)生，如下所示： 由縱向平面的半軸連接產(chǎn)生的間接反應(yīng) 因為扭轉(zhuǎn)力傳遞沒有損失并且 兩個在連接軸上的第二個力矩都相互vwd 補(bǔ)償。然而，事實上（有扭轉(zhuǎn)力損失） ，第二個力矩出現(xiàn)不同： 21DWWM 2T 第二個力矩不同點是： 2 2()tan/2sinta/tanDWVDWvwWvwTT 為了簡化應(yīng)用給出 和fVD(ta/1si/ta)DWvvvMTA 需要在兩個連接處都有抵抗反應(yīng)的力這里 。由連接處引起的干擾常數(shù) f，一個附加的轉(zhuǎn)向裝置扭轉(zhuǎn)力矩也圍/DWFL 繞著主銷軸線變動： cos/fDWTMfA 這里 每個車輪的轉(zhuǎn)向裝置扭轉(zhuǎn)力矩f 轉(zhuǎn)向裝置扭轉(zhuǎn)力矩差f f連接處干擾系數(shù) L連接軸（半軸）的長度 由于 f 值小，理想值是 0， 的影響較小。fT 5 轉(zhuǎn)彎時的效應(yīng) 扭轉(zhuǎn)時由于驅(qū)動輪的速度不相等，黏性連接器也提供一個自瑣的扭轉(zhuǎn)力矩。 在平穩(wěn)轉(zhuǎn)向過程中，速度較慢的內(nèi)側(cè)車輪被外側(cè)車輪黏性連接器施加的一個附加 的驅(qū)動力。 前輪驅(qū)動力的汽車穩(wěn)定狀態(tài)下轉(zhuǎn)向時的牽引力。 不同的牽引力 和 導(dǎo)致一個側(cè)偏力矩 MCOG，它必須被一個較大的側(cè)偏flDrfl 力補(bǔ)償，因此在前軸有一個大的滑動角 af。因此前驅(qū)動輪的汽車自動轉(zhuǎn)向裝置上 黏性連接器的影響趨向一個在轉(zhuǎn)向裝置狀態(tài)下的特性。這個運(yùn)動方式整體上和所 有轉(zhuǎn)向操縱下在穩(wěn)定狀態(tài)下轉(zhuǎn)彎移動時的現(xiàn)代汽車操縱方式的偏重心相一致.合適 的試驗結(jié)果如圖表 11 所示。 安裝有開式差速器的汽車餓安裝有黏性連接器的汽車在穩(wěn)定狀態(tài)下轉(zhuǎn)彎時的 對比 所示在轉(zhuǎn)彎時不對稱的牽引力干擾也會改進(jìn)汽車的直線行駛。每一次偏離正 常的直線方向都會引起車輪以輕微的不同半徑滾動。驅(qū)動力和產(chǎn)生的側(cè)偏力矩差 會使汽車重新回到直線行駛。 雖然這些方向的偏離引起僅僅很小的車輪滾動半徑差，但是旋轉(zhuǎn)的偏差尤其 在高速時對于一個黏性連接器前差速器是足夠?qū)⑵噹У街本€上行駛的。 安裝有開式差速器的高動力前輪驅(qū)動汽車當(dāng)以低檔加速離開緊急轉(zhuǎn)角時通常 旋轉(zhuǎn)它們的內(nèi)側(cè)車輪。安裝有限制滑動黏性差速器，這個旋轉(zhuǎn)是有限的并且有不 同車輪的速度差產(chǎn)生的扭轉(zhuǎn)力為外側(cè)的驅(qū)動輪提供附加的牽引力效果。 裝有黏性限制滑動差速器的前輪驅(qū)動汽車在轉(zhuǎn)道上加速時的牽引力 特別地當(dāng)行駛或加速離開一個 T 形交叉路口加速能力就這樣被改善（也就是 說在 T 形路口橫切向右或向左從停止位置加速） 。 顯示了裝有開式差速器和裝有黏性限制滑動差速器在穩(wěn)定狀態(tài)下轉(zhuǎn)彎過程中 加速試驗的結(jié)果。 裝有一個開式差速器的前輪驅(qū)動汽車在半徑為 40m 的濕瀝青彎曲路面上加速 特性（實驗過程中安裝有轉(zhuǎn)向裝置輪角測試儀） 裝有一個黏性連接器的前輪驅(qū)動汽車在半徑為 40m 的濕瀝青彎曲路面上加速 特性（實驗過程中安裝有轉(zhuǎn)向裝置輪角測試儀） 安裝有一個開式差速器的汽車平均加速度為 同時裝有黏性連接CSDM2.0/ms 器的汽車平均加速度達(dá)到 （被發(fā)動機(jī)功率限制） 。在這些試驗中，由內(nèi)側(cè)2.3/ms 的從動輪引起的最大速度差，被從帶有開式差速器的 240rpm 減少到帶有黏性連接 器的 100rpm。 在彎道上加速行駛時，前輪驅(qū)動的汽車通常處在操縱狀態(tài)下要多于其勻速行 駛的狀態(tài)。前輪傳遞側(cè)偏力潛能降低的原理是由于重心移到后軸車輪并且在驅(qū)動 輪上增加了縱向力。在一個開式環(huán)形控制循環(huán)測試中這個能夠看出在開始加速以 后（時間為 0 在圖表 13 和 14 中）偏跑速度（跑偏率）的降低。從圖表 13 和 14 中還可以看出開始加速時裝有開式差速器汽車的跑偏率比裝有黏性連接器汽車的 下降的更快。然而，在開始加速大約 2 秒后，黏性連接的汽車的跑偏率下降斜率 增加高于裝有開式差速器 的汽車。 安裝有限制滑動前差速器的汽車在轉(zhuǎn)彎過程中加速時具有一個更穩(wěn)定的最初 反應(yīng)比裝有開式差速器的汽車，降低它的操縱狀態(tài)。這是因為內(nèi)側(cè)驅(qū)動輪的高滑 動通過黏性連接器產(chǎn)生一個增加的驅(qū)動力到外側(cè)車輪。前輪牽引力的不平衡導(dǎo)致 在行駛方向上的偏跑力矩 ，反對操縱狀態(tài)。CSDM 當(dāng)驅(qū)動輪的附著限制是超出的,安裝黏性連接器的汽車處于操縱狀態(tài)比安裝有 開式差速器的汽車更明顯(這里,開始加速后 2 秒)。在非常低的摩擦力表面，例如 雪或者冰，當(dāng)裝有限制滑動差速器的汽車在曲線路面上加速時更強(qiáng)的操縱性被期 望因為通過黏性連接器連接的驅(qū)動輪更容易旋轉(zhuǎn)（動力轉(zhuǎn)向裝置） 。然而，這個特 性能很容易地被駕駛員或者自動節(jié)氣門調(diào)節(jié)牽引系統(tǒng)控制。在這些情況下比后輪 驅(qū)動的汽車更容易控制。在轉(zhuǎn)彎過程中當(dāng)加速時它能夠防止動力過分操縱。考慮 到，所有的情況，裝配有一個黏性連接器的汽車在加速過程中具有穩(wěn)定的加速行 動方式在光滑路面上只有小的缺點。 通過突然釋放加速器，在轉(zhuǎn)彎過程中節(jié)氣門關(guān)閉的反應(yīng)，通常導(dǎo)致前輪驅(qū)動 的汽車改換方向（節(jié)氣門關(guān)閉超出了操縱） 。高動力的模型能得到高側(cè)偏加速度顯 示出最大規(guī)模的反應(yīng)。這個節(jié)氣門關(guān)閉反應(yīng)有幾個原因例如運(yùn)動學(xué)上的影響，或 者，當(dāng)汽車降低速度試著以一個較小的轉(zhuǎn)變半徑通過時。然而，實質(zhì)上的原因， 是動力的重心從后軸轉(zhuǎn)移到前軸，這會導(dǎo)致前軸降低滑動角。后軸增加滑動角。 因為，后軸車輪不傳遞驅(qū)動力矩，在這種情況下在后軸上的影響比前軸上的影響 更大。在節(jié)氣門關(guān)閉之前。 。 安裝有黏性限制滑動差速器前輪驅(qū)動的汽車當(dāng)轉(zhuǎn)變時關(guān)閉節(jié)氣門后移動立刻 產(chǎn)生的制動力 隨著內(nèi)側(cè)的車輪繼續(xù)比外側(cè)車輪更慢的轉(zhuǎn)動，黏性聯(lián)結(jié)器給外側(cè)車輪提供更 大的制動力 。由于前輪力的不同圍繞著汽車重量的中心會產(chǎn)生一個抵消正常fB 轉(zhuǎn)向反應(yīng)的側(cè)偏力矩 MCOG.。 將安裝有開式差速器的汽車和裝有黏性聯(lián)結(jié)器的在關(guān)閉節(jié)氣門的移動過程中 轉(zhuǎn)向方式進(jìn)行比較時，如圖表 16 和 17 所示，安裝有黏性差速器的兩個驅(qū)動輪子 之間速度差是降低的。 在轉(zhuǎn)彎半徑為 40 米（不封閉的環(huán)形）的濕瀝青路面上安裝有開式差速器前輪 驅(qū)動汽車的節(jié)氣門關(guān)閉特性 在轉(zhuǎn)彎半徑為 40 米（不封閉的環(huán)形）的濕瀝青路面上安裝有黏性聯(lián)結(jié)器前輪 驅(qū)動汽車的節(jié)氣門關(guān)閉特性 安裝有開式差速器的汽車側(cè)偏速度（側(cè)偏率） ，和相對的側(cè)偏角（除汽車保持 繼續(xù)在穩(wěn)定狀態(tài)下轉(zhuǎn)彎的側(cè)偏角之外）在節(jié)氣門關(guān)閉后（時間為零如圖表 14 和 15）顯示一個非常明顯的增加。在安裝有一個黏性的限制滑動差速器的汽車上節(jié) 氣門關(guān)閉后側(cè)偏率的突然增加和相對側(cè)偏角的增加都有很大的降低。 例如在一個彎道上隨著半徑的增加，一上正常的駕駛一個超大號的前輪驅(qū)動 汽車的人通常僅僅的慣常的空檔的操縱裝置下的汽車操縱方式，然后駕駛員忽然 驚奇并且在節(jié)氣門突然的釋放后會有有力的操縱反應(yīng)。如果駕駛員對情況的反應(yīng) 不正確汽車將進(jìn)一步惡化汽車離開車道到曲線的內(nèi)側(cè)的事故是這個事件的驗證。 因此黏性聯(lián)結(jié)器為一個正常的駕駛員改善節(jié)氣門關(guān)閉的行為方式當(dāng)保持可控制， 可預(yù)言的并且安全駕駛時。 7 總結(jié) 總之，黏性聯(lián)結(jié)器在前軸差速器的試用能被證實。它也明確地影響整個汽車 的控制和穩(wěn)定，只是稍微地，但是可以接受的在扭轉(zhuǎn)力操縱上的影響。 為了減小不想要的扭轉(zhuǎn)力操縱的影響一個基本的設(shè)計準(zhǔn)則被給出： 1 由于縱向載荷改變產(chǎn)生的警覺反應(yīng)必須盡可能的小 2 主銷軸線和車輪中心之間的距離必須盡可能的小 3 垂直彎曲角變化范圍應(yīng)該接近零（或者為負(fù)值） 4 兩側(cè)的垂直彎曲角應(yīng)該一樣 5 側(cè)軸應(yīng)該等長 扭轉(zhuǎn)力操縱上最小影響是聯(lián)結(jié)處干擾常數(shù)的理想值為零。帶有和不帶有 ABS 制動，僅對黏性聯(lián)結(jié)器僅有輕微的影響。在前輪驅(qū)動的汽車上，黏性限制滑動差 速器顯著提高了牽引力。 有獨(dú)立轉(zhuǎn)向裝置的前輪驅(qū)動汽車，在轉(zhuǎn)向時會輕微影響?zhàn)ば韵拗苹瑒硬钏倨鳌?前軸安裝有黏性聯(lián)結(jié)器的汽車，在轉(zhuǎn)彎過程中關(guān)閉氣門和改進(jìn)加速的措施，使汽 車更穩(wěn)定而且更安全。 附件 2：外文原文 The Effect of a Viscous Coupling Used as a Front-Wheel Drive Limited-Slip Differential on Vehicle Traction and Handling 1 ABCTRACT The viscous coupling is known mainly as a driveline component in four wheel drive vehicles. Developments in recent years, however, point toward the probability that this device will become a major player in mainstream front-wheel drive application. Production application in European and Japanese front-wheel drive cars have demonstrated that viscous couplings provide substantial improvements not only in traction on slippery surfaces but also in handing and stability even under normal driving conditions. This paper presents a serious of proving ground tests which investigate the effects of a viscous coupling in a front-wheel drive vehicle on traction and handing. Testing demonstrates substantial traction improvements while only slightly influencing steering torque. Factors affecting this steering torque in front-wheel drive vehicles during straight line driving are described. Key vehicle design parameters are identified which greatly influence the compatibility of limited-slip differentials in front-wheel drive vehicles. Cornering tests show the influence of the viscous coupling on the self steering behavior of a front-wheel drive vehicle. Further testing demonstrates that a vehicle with a viscous limited-slip differential exhibits an improved stability under acceleration and throttle-off maneuvers during cornering. 2 THE VISCOUS COUPLING The viscous coupling is a well known component in drivetrains. In this paper only a short summary of its basic function and principle shall be given. The viscous coupling operates according to the principle of fluid friction, and is thus dependent on speed difference. As shown in Figure 1 the viscous coupling has slip controlling properties in contrast to torque sensing systems. This means that the drive torque which is transmitted to the front wheels is automatically controlled in the sense of an optimized torque distribution. In a front-wheel drive vehicle the viscous coupling can be installed inside the differential or externally on an intermediate shaft. This layout has some significant advantages over the internal solution. First, there is usually enough space available in the area of the intermediate shaft to provide the required viscous characteristic. This is in contrast to the limited space left in todays front-axle differentials. Further, only minimal modification to the differential carrier and transmission case is required. In-house production of differentials is thus only slightly affected. Introduction as an option can be made easily especially when the shaft and the viscous unit is supplied as a complete unit. Finally, the intermediate shaft makes it possible to provide for sideshafts of equal length with transversely installed engines which are important to reduce torque steer. This special design also gives a good possibility for significant weight and cost reductions of the viscous unit. GKN Viscodrive is developing a low weight and cost viscous coupling. By using only two standardized outer diameters, standardized plates, plastic hubs and extruded material for the housing which can easily be cut to different lengths, it is possible to utilize a wide range of viscous characteristics. 3 TRACTION EFFECTS As a torque balancing device, an open differential provides equal tractive effort to both driving wheels. It allows each wheel to rotate at different speeds during cornering without torsional wind-up. These characteristics, however, can be disadvantageous when adhesion variations between the left and right sides of the road surface (split-) limits the torque transmitted for both wheels to that which can be supported by the low- wheel. With a viscous limited-slip differential, it is possible to utilize the higher adhesion potential of the wheel on the high-surface. When for example, the maximum transmittable torque for one wheel is exceeded on a split-surface or during cornering with high lateral acceleration, a speed difference between the two driving wheels occurs. The resulting self-locking torque in the viscous coupling resists any further increase in speed difference and transmits the appropriate torque to the wheel with the better traction potential. It can be seen in Figure 4 that the difference in the tractive forces results in a yawing moment which tries to turn the vehicle in to the low-side, To keep the vehicle in a straight line the driver has to compensate this with opposite steering input. Though the fluid-friction principle of the viscous coupling and the resulting soft transition from open to locking action, this is easily possible. Reported are the average steering-wheel torque Ts and the average corrective opposite steering input required to maintain a straight course during acceleration on a split-track with an open and a viscous differential. The differences between the values with the open differential and those with the viscous coupling are relatively large in comparison to each other. However, they are small in absolute terms. Subjectively, the steering influence is nearly unnoticeable. The torque steer is also influenced by several kinematic parameters which will be explained in the next section of this paper. 5EFFECT ON CORNERING Viscous couplings also provide a self-locking torque when cornering, due to speed differences between the driving wheels. During steady state cornering, as shown in figure 10, the slower inside wheel tends to be additionally driven through the viscous coupling by the outside wheel. Tractive forces for a front-wheel drive vehicle during steady state cornering The difference between the Tractive forces Dfr and Dfl results in a yaw moment MCOG, which has to be compensated by a higher lateral force, and hence a larger slip angle af at the front axle. Thus the influence of a viscous coupling in a front-wheel drive vehicle on self-steering tends towards an understeering characteristic. This behavior is totally consistent with the handling bias of modern vehicles which all under steer during steady state cornering maneuvers. Appropriate test results are shown in figure 11. Figure 11: comparison between vehicles fitted with an open differential and viscous coupling during steady state cornering. The asymmetric distribution of the tractive forces during cornering as shown in figure 10 improves also the straight-line running. Every deviation from the straight-line position causes the wheels to roll on slightly different radii. The difference between the driving forces and the resulting yaw moment tries to restore the vehicle to straight-line running again. Although these directional deviations result in only small differences in wheel travel radii, the rotational differences especially at high speeds are large enough for a viscous coupling front differential to bring improvements in straight-line running. High powered front-wheel drive vehicles fitted with open differentials often spin their inside wheels when accelerating out of tight corners in low gear. In vehicles fitted with limited-slip viscous differentials, this spinning is limited and the torque generated by the speed difference between the wheels provides additional tractive effort for the outside driving wheel. Tractate forces for a front-wheel drive vehicle with viscous limited-slip differential during acceleration in a bend The acceleration capacity is thus improved, particularly when turning or accelerating out of a T-junction maneuver (i.e. accelerating from a stopped position at a “T” intersection-right or left turn). the results of acceleration tests during steady state cornering with an open differential and with viscous limited-slip differential. Accelerations characteristic for a front-wheel drive vehicle with an open differential on wet asphalt at a radius of 40m (fixed steering wheel angle throughout test). Acceleration Characteristics for a Front-Wheel Drive Vehicle with Viscous Coupling on Wet Asphalt at a Radius of 40m (Fixed steering wheel angle throughout test) The vehicle with an open differential achieves an average acceleration of 2.0 2/sm while the vehicle with the viscous coupling reaches an average of 2.3 (limited by 2/s engine-power). In these tests, the maximum speed difference, caused by spinning of the inside driven wheel was reduced from 240 rpm with open differential to 100 rpm with the viscous coupling. During acceleration in a bend, front-wheel drive vehicles in general tend to understeer more than when running at a steady speed. The reason for this is the reduction of the potential to transmit lateral forces at the front-tires due to weight transfer to the rear wheels and increased longitudinal forces at the driving wheels. In an open loop control-circle-test this can be seen in the drop of the yawing speed (yaw rate) after starting to accelerate (Time 0 in Figure 13 and 14). It can also be taken from Figure 13 and Figure 14 that the yaw rate of the vehicle with the open differential falls-off more rapidly than for the vehicle with the viscous coupling starting to accelerate. Approximately 2 seconds after starting to accelerate, however, the yaw rate fall-off gradient of the viscous-coupled vehicle increases more than at the vehicle with open differential. The vehicle with the limited slip front differential thus has a more stable initial reaction under accelerating during cornering than the vehicle with the open differential, reducing its understeer. This is due to the higher slip at the inside driving wheel causing an increase in driving force through the viscous coupling to the outside wheel. The imbalance in the front wheel tractive forces results in a yaw moment acting in CSDM direction of the turn, countering the understeer. When the adhesion limits of the driving wheels are exceed, the vehicle with the viscous coupling understeers more noticeably than the vehicle with the open differential (here, 2 seconds after starting to accelerate). On very low friction surfaces, such as snow or ice, stronger understeer is to be expected when accelerating in a curve with a limited slip differential because the driving wheels-connected through the viscous coupling-can be made to spin more easily (power-under-steering). This characteristic can, however, be easily controlied by the driver or by an automatic throttle modulating traction control system. Under these conditions a much easier to control than a rear-wheel drive car. Which can exhibit power-oversteering when accelerating during cornering. All things, considered, the advantage through the stabilized acceleration behavior of a viscous coupling equipped vehicle during acceleration the small disadvantage on slippery surfaces. Throttle-off reactions during cornering, caused by releasing the accelerator suddenly, usually result in a front-wheel drive vehicle turning into the turn (throttle-off oversteering ). High-powered modeles which can reach high lateral accelerations show the heaviest reactions. This throttle-off reaction has several causes such as kinematic influence, or as the vehicle attempting to travel on a smaller cornering radius with reducing speed. The essential reason, however, is the dynamic weight transfer from the rear to the front axle, which results in reduced slip-angles on the front and increased slip-angles on the rear wheels. Because the rear wheels are not transmitting driving torque, the influence on the rear axle in this case is greater than that of the front axle. The driving forces on the front wheels before throttle-off (see Figure 10) become over running or braking forces afterwards. Baraking Forces for a Front-Wheel Drive Vehicle with Viscous Limited-Slip Differential Immediately after a Throttle-off Maneuver While Cornering As the inner wheel continued to turn more slowly than the outer wheel, the viscous coupling provides the outer wheel with the larger braking force . The force difference fB between the front-wheels applied around the center of gravity of the vehicle causes a yaw moment that counteracts the normal turn-in reaction.GCM0 When cornering behavior during a throttle-off maneuver is compared for vehicles with open differentials and viscous couplings, as shown in Figure 16 and 17, the speed difference between the two driving wheels is reduced with a viscous differential. Throttle-off Characteristics for a Front-Wheel Drive Vehicle with an open Differential on Wet Asphalt at a Radius of 40m (Open Loop) Throttle-off Characteristics for a Front-Wheel Drive Vehicle with Viscous Coupling on Wet Asphalt at a Radius of 40m (Open Loop) The yawing speed (yaw rate), and the relative yawing angle (in addition to the yaw angle which the vehicle would have maintained in case of continued steady state cornering) show a pronounced increase after throttle-off (Time=0 seconds in Figure 14 and 15) with the open differential. Both the sudden increase of the yaw rate after throttle- off and also the increase of the relative yaw angle are significantly reduced in the vehicle equipped with a viscous limited-slip differential. A normal driver os a front-wheel drive vehicle is usually only accustomed to neutral and understeering vehicle handing behavior, the driver can then be surprised by sudden and forceful oversteering reaction after an abrupt release of the throttle, for example in a bend with decreasing radius. This vehicle reaction is further worsened if the driver over- corrects for the situation. Accidents where cars leave the road to the inner side of the curve is proof of this occurrence. Hence the viscous coupling improves the throttle-off behavior while remaining co