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理工科類
本科生畢業(yè)設(shè)計(論文)開題報告
論文(設(shè)計)題目
純電動跑車變速箱設(shè)計
作者所在系別
機電工程
作者所在專業(yè)
車輛工程
作者所在班級
B13142
作 者 姓 名
鄭廷蕓
作 者 學 號
201322198
指導教師姓名
白亞雙
指導教師職稱
講師
完 成 時 間
2017
年
3
月
北華航天工業(yè)學院教務(wù)處制
說 明
1.根據(jù)學?!懂厴I(yè)設(shè)計(論文)工作暫行規(guī)定》,學生必須撰寫《畢業(yè)設(shè)計(論文)開題報告》。開題報告作為畢業(yè)設(shè)計(論文)答辯委員會對學生答辯資格審查的依據(jù)材料之一。
2.開題報告應(yīng)在指導教師指導下,由學生在畢業(yè)設(shè)計(論文)工作前期內(nèi)完成,經(jīng)指導教師簽署意見及所在專業(yè)教研室論證審查后生效。開題報告不合格者需重做。
3.畢業(yè)設(shè)計開題報告各項內(nèi)容要實事求是,逐條認真填寫。其中的文字表達要明確、嚴謹,語言通順,外來語要同時用原文和中文表達。第一次出現(xiàn)縮寫詞,須注出全稱。
4.開題報告中除最后一頁外均由學生填寫,填寫各欄目時可根據(jù)內(nèi)容另加附頁。
5.閱讀的主要參考文獻應(yīng)在10篇以上(土建類專業(yè)文獻篇數(shù)可酌減),其中外文資料應(yīng)占一定比例。本學科的基礎(chǔ)和專業(yè)課教材一般不應(yīng)列為參考資料。
6.參考文獻的書寫應(yīng)遵循畢業(yè)設(shè)計(論文)撰寫規(guī)范要求。
7.開題報告應(yīng)與文獻綜述、一篇外文譯文和外文原文復印件同時提交,文獻綜述的撰寫格式按畢業(yè)設(shè)計(論文)撰寫規(guī)范的要求,字數(shù)在2000字左右。
畢業(yè)設(shè)計(論文)開題報告
學生姓名
鄭廷蕓
專 業(yè)
車輛工程
班 級
B13142
指導教師姓名
白亞雙
職 稱
講師
工作單位
課題來源
課題性質(zhì)
課題名稱
純電動跑車變速箱設(shè)計
3
本設(shè)計的科學依據(jù)
(科學意義和應(yīng)用前景,國內(nèi)外研究概況,目前技術(shù)現(xiàn)狀、水平和發(fā)展趨勢等)
隨著石油資源的日益減少和環(huán)境保護要求的提高,電動汽車的發(fā)展越來越受到人們的重視,然而,對動力傳動系統(tǒng)部件的設(shè)計參數(shù)進行研究是提高電動汽車性能的重要手段之一。變速器是汽車重要的傳動系組成,在較大范圍內(nèi)改變汽車行駛速度的大小和汽車驅(qū)動輪上
扭矩的大小。
電動汽車的變速器與普通變速器相比,其結(jié)構(gòu)有所不同。因為驅(qū)動電機的旋向可以通過電路控制實現(xiàn)變換,所以電動汽車無需內(nèi)燃機汽車變速器中的倒檔而設(shè)置倒檔軸,只需應(yīng)用電機反轉(zhuǎn)來實現(xiàn)倒車行駛。設(shè)計中利用已知參數(shù)確定變速器各參數(shù),對軸和各擋齒輪進行校核,繪制出裝配圖及零件圖。
同時本設(shè)計對電動汽車的動力傳動系統(tǒng)進行了匹配設(shè)計計算,計算結(jié)果表明達到性能要求。
設(shè)計內(nèi)容和預(yù)期成果
(具體設(shè)計內(nèi)容和重點解決的技術(shù)問題、預(yù)期成果和提供的形式)
1)傳動機構(gòu)布置方案分析
變速器傳動機構(gòu)有兩種分類方法。根據(jù)軸的形式不同,分為固定軸式和旋轉(zhuǎn)軸式(常配合行星齒輪傳動)兩類。固定軸式又分為兩軸式,中間軸式.雙中間軸式變速器。固定軸式應(yīng)用廣泛,。其中兩軸式變速器多用于發(fā)動機前置前輪驅(qū)動的汽車上。中間軸式變速器多用于發(fā)動機前置后輪驅(qū)動的汽車上。旋轉(zhuǎn)軸式主要用于液壓機械式變速囂。與中間軸式變速囂比較,兩軸式具有結(jié)構(gòu)簡單,輪廓尺寸小,布置方便。此外,因為其經(jīng)過一對齒輪嚙合傳動動力,故傳動效率高同時噪音低。三軸式變速囂與兩軸式相比各檔多了一對齒輪傳動因而傳遞效率低噪音大。所以選擇本設(shè)計兩軸式雙擋變速器。
2)變速其主要參數(shù)選擇
(l)擋數(shù)
增加變速器的檔數(shù)能改善汽車的動力性和經(jīng)濟性,擋數(shù)越多,變速器的結(jié)構(gòu)越復雜,并且是尺寸輪廓和質(zhì)量加大.同時操縱機構(gòu)復雜,而且在使用時換擋頻率也增高.由于電動汽車的發(fā)展起步晚,受技術(shù)限制所以選用兩擋變速箱,倒擋由電機反轉(zhuǎn)來實現(xiàn)。
(2)傳動比范圍
變速器的傳動比范圍是指變速器最低檔傳動比與最高檔轉(zhuǎn)動比的比值.傳動比范圍的確定與選定的發(fā)動機參數(shù),汽車的最高車速和使用條件等因素有關(guān)。
(3)中心距A
對兩軸式變速器,輸入軸與第二軸之間的距離稱為變速器中心距,其大小不僅對變速器的外形尺寸,體積和質(zhì)量大小,而日對輪齒的接觸強度有影響。中心距越小,齒輪的接觸應(yīng)力大,齒輪壽命短。最小允許中心距當有保證齒輪有必要的接觸強度來確定。
(4)各檔齒輪齒數(shù)的分配
在初選中心距,齒輪模數(shù)和螺旋角以后.可更據(jù)變速器的擋數(shù),傳動比和傳動方案來分配各檔齒輪的齒數(shù)。兩檔變速器為例,說明分配齒數(shù)的方法.盡可能使各檔齒輪的齒數(shù)比應(yīng)該不是整數(shù)。
3)變速器的設(shè)計與計算
(1)齒輪的損環(huán)形式
輪齒折斷,齒面疲勞剝落,移動換擋齒輪端部破壞,
輪齒折斷分兩種:輪齒受足夠大的沖擊載荷作用,造成輪齒彎曲折斷;輪齒再重復載荷作用下齒根產(chǎn)生疲勞裂紋,裂紋擴展深度逐漸加大,然后出現(xiàn)彎曲折斷。前者在變速器中出現(xiàn)的很少,后看出現(xiàn)的多。
(2)齒輪強度計算
與其他機械行業(yè)相比,不同用途汽車的變速器齒輪使用田間仍是相似的。此外,機車變速器齒輪用的材抖,熱處理方法,加工方法,精度級別,支承方式也基本一致。如汽車變速器齒輪用低碳鋼制作,采用剃齒與磨齒精加工,齒輪表面采用溶碳淬火熱處理工
藝,齒輪精度為JBI79-83,6級和7級。
4)軸承的選擇
變速器軸承常采用圓柱滾子軸承,球軸承,滾針軸承,圓錐滾子軸承,滑動軸套等。至于何處應(yīng)當采用何種軸承,是受結(jié)構(gòu)限制并隨所承受的載荷特點不同而不同。
汽車變速器結(jié)構(gòu)緊湊,尺寸小,采用尺寸大些的軸承結(jié)構(gòu)受限制,常在布置上有困難。如變速器的第二軸前端支承在第一軸常嚙合齒輪的內(nèi)腔中,內(nèi)腔尺寸足夠時可布置圓柱滾子軸承,若空間不足則采用滾針軸承.變速器笫一軸前端支承在飛輪的內(nèi)腔里,因有足夠大的空間常采用球軸承來承受向力。
5)變速器操縱機構(gòu)
根據(jù)汽車使用條件的需要駕駛員利用變速器的操縱機構(gòu)完成選擋和實現(xiàn)換擋或退到空擋的工作。
變速器操縱機構(gòu)應(yīng)當滿足如下主要要求:換擋時只能掛入一個擋位,換擋后應(yīng)使齒輪在全齒長上嚙合,防止自動脫擋或自動掛擋,防止誤掛倒擋,換擋輕便。
用于機械式變速器的操縱機構(gòu),常見的是由變速軒,撥塊,撥叉、變速叉軸及互鎖、自鎖和倒擋鎖裝置等主要件組成,并依靠駕駛員手力完成換擋或退到空擋工作,稱為手動換擋變速器。
本科生畢業(yè)設(shè)計(論文)文獻綜述
設(shè)計 (論文)題目
純電動汽車變速箱構(gòu)設(shè)
計
作者所在系別
機電工程
作者所在專業(yè)
車輛工程
作者所在班級
B13142
作 者 姓 名
鄭廷蕓
作 者 學 號
201322198
指導教師姓名
白亞雙
指導教師職稱
講師
完 成 時 間
2017
年
3
月
北華航天工業(yè)學院教務(wù)處制
說 明
1.根據(jù)學?!懂厴I(yè)設(shè)計(論文)工作暫行規(guī)定》,學生必須撰寫畢業(yè)設(shè)計(論文)文獻綜述。文獻綜述作為畢業(yè)設(shè)計(論文)答辯委員會對學生答辯資格審查的依據(jù)材料之一。
2.文獻綜述應(yīng)在指導教師指導下,由學生在畢業(yè)設(shè)計(論文)工作前期內(nèi)完成,由指導教師簽署意見并經(jīng)所在專業(yè)教研室審查。
3.文獻綜述各項內(nèi)容要實事求是,文字表達要明確、嚴謹,語言通順,外來語要同時用原文和中文表達。第一次出現(xiàn)縮寫詞,須注出全稱。
4.學生撰寫文獻綜述,閱讀的主要參考文獻應(yīng)在10篇以上(土建類專業(yè)文獻篇數(shù)可酌減),其中外文資料應(yīng)占一定比例。本學科的基礎(chǔ)和專業(yè)課教材一般不應(yīng)列為參考資料。
5.文獻綜述的撰寫格式按畢業(yè)設(shè)計(論文)撰寫規(guī)范的要求,字數(shù)在2000字左右。文獻綜述應(yīng)與開題報告同時提交。
畢 業(yè) 設(shè) 計(論 文)文 獻 綜 述
摘要
變速器是汽車傳動系統(tǒng)結(jié)構(gòu)中最重要的部分之一,汽車的前進、后退,增速、減速都要靠變速器傳動來實現(xiàn)。而且變速器在汽車動力性和燃油經(jīng)濟性上也有重要的影響。
本設(shè)計的電動賽車變速器,主要任務(wù)是完成齒輪、軸、箱體等的設(shè)計及校核,和位置的確定,并滿足其承載能力的同步器。另外,針對齒輪作用力的不同,可以在不同的軸上選擇合適的軸承。利用AUTCAD完成變速器的總成圖、第一軸、第二軸、中間軸、各個擋齒輪及同步器的設(shè)計。
隨著我國汽車行業(yè)的迅猛發(fā)展,人們對汽車的需求也越來越高。通過對載貨汽車變速器的設(shè)計我了解到變速器在汽車結(jié)構(gòu)中具有著重要的作用。變速器結(jié)構(gòu)的改進對汽車行業(yè)的發(fā)展與進步具有著深遠的意義。
關(guān)鍵詞:純電動汽車 零排放 蓄電池
Abstract
Transmission is the most important part in transmission agent in an auto. The reason is that forward, backward, speed up, slowdown and other manipulate of auto have to be completed by transmission. And transmission is also important in Automotive dynamica perform and fuel economy.
The main purpose of this design--電動賽車 gearbox is to complete the design, check and position among gears, axles, case, and this design should have enough capability. In addition, it can choose an appropriate bearing, which based on the different gears’ forces. We can complete this design, primary shaft, secondary shaft, intermediate shaft, any gear, and synchro by AUTCAD.
With the rapid development of Chinese automobile industry, people has more and more demands in autoes. To design this transmission of van; I realized that transmission is very important in van’s conformation. The developed of transmission is profound for growth and progress of autoes.
Key words: Electric Vehicle, Zero Emissions, Battery
1.電動汽車的發(fā)展概況
從汽車發(fā)展的歷史來看電動汽車(EV,Electric Vehicle)其實比燃油汽車還要早誕生幾年,但受電池和驅(qū)動控制技術(shù)的局限,其發(fā)展卻遠遠落后于燃油汽車。本世紀六七十年代,電動汽車開始復蘇?,F(xiàn)在隨著電力電子、控制、材料等技術(shù)的發(fā)展在世界各國激發(fā)了研究、開發(fā)、應(yīng)用電動汽車的熱潮,可以預(yù)見電動汽車將是21世紀的重要交通工具。國外的發(fā)展狀況,德、日、法、美這幾個汽車工業(yè)發(fā)達國家,到目前為止都已研制出實用的電動汽車,其中包括大客車、轎車、摩托車等。美國幾大主要汽車制造商已廣泛深入的開展了電動車的研究。其中通用汽車公司是電動汽車行業(yè)的領(lǐng)導者。通用與美國能源部合作,用MH-Ni電池取代鉛蓄電池,使電動車一次充電行使距離達到160km,他們計劃在2004年開始生產(chǎn)燃料電池的電動汽車。1991年美國三大汽車公司簽訂協(xié)議,合作研究電動汽車用先進電池,成立先進電池聯(lián)合體。同年7月美國電力研究院參加了美國先進電池聯(lián)合體,10月布什總統(tǒng)批準了226億美元撥款資助此項研究。福特汽車公司投資15億英磅開發(fā)電動汽車,1993年研制成功,現(xiàn)已生產(chǎn)81輛,分赴美國各地進行試運行,采用480個鈉硫單元電池,取代原來的鉛酸蓄電池。通用汽車公司1990年在洛杉磯展出“沖擊”電動驕車,1994年生產(chǎn)50輛。1991年1月美國電力研究院,1995年美電力研究院、克萊斯勒公司與南加州愛迪生公司共同開發(fā)50輛電動貨車。1995年3月統(tǒng)計數(shù)據(jù),美國現(xiàn)有190家電動汽車生產(chǎn)企業(yè),共有電動汽車2000多輛。
日本東京電力公司1988年聯(lián)合日本電池公司共同開發(fā)TZA電動汽車,體現(xiàn)了當時最新技術(shù)水平,空載量1573kg,裝有288v鎳鎘電池,四臺直流無刷電機,輸出功率為100kW,最高車速176km/h。
法國標致一一一雪鐵龍與雷諾兩大汽車公司一直在積極研制,1990年的J-5和C-25電動貨車投入生產(chǎn),1995年將標致106和雪鐵龍AX電動車投入生產(chǎn)。法國能源部、標致一一一雪鐵龍公司和羅切里市簽訂協(xié)議從1993年9月開始,該市試用標致106和雪鐵龍AX改裝的電動轎車各25輛,并在市建9個公共地面充電站,3個快速充電站,1994年7月50輛電動轎車己行駛32.7萬公里,法國政府計劃在巴黎等27個城市中繼續(xù)推廣電動車。
德國早在1900年波許公司就生產(chǎn)早期的電動汽車。1972年開始歐寶公司研制電動汽車,1981年與ABB公司合作改裝電動車。80年代初期奔馳生產(chǎn)電動大客車,至今還有十輛在運行中。德國政府科技部資助17億馬克開發(fā)電動汽車,19m年科爾州將300輛電動汽車投入運行,德國奔馳、大眾兩大汽車集團合資建立開發(fā)機構(gòu)。
其他國家和地區(qū)如丹麥、奧地利、捷克、匈牙利、俄羅斯、澳大利業(yè)、墨西哥等都在開展和研制電動汽車。特別值得關(guān)注的是業(yè)洲許多新發(fā)展國家和地區(qū),近30年來經(jīng)濟發(fā)展迅速,人民生活提高很快,80年代中國香港從歐洲及日本進口15輛電動汽車,1983年香港政府通過規(guī)定,免除電動汽車的首次登記稅,即電動汽車價格為燃油車二倍時也與燃油車價格相當;泰國每月出售500輛電動三輪車;馬來西業(yè)1995年投產(chǎn);中國臺灣1987年開始中華汽車公司外銷電動車。業(yè)洲電動汽車發(fā)展的前景令人樂觀。
我國電動汽車發(fā)展狀況。本世紀40年代重慶進行過電動汽車的研究與試驗,條件所限未能實現(xiàn)。1958年研制工作半途而廢,在1962年上海公用事業(yè)研究所進行蓄電池微型汽車研究,制成SWD-S2電動汽車滿載量為968Kg,電機功率為2.5,蓄電池比能量為23.8Wh/kg。行駛車速達到284km/h。一次充電持續(xù)行程為82.8km,實際運行了幾千公里。電池循環(huán)壽命達110次,當時該車每百公里耗電費為1.95元,蓄電池折舊費為8.6元。當時汽油車每公里汽油消耗費為3.65元,由于蓄電池技術(shù)沒過關(guān),壽命太短,不得不終止。在70年代,研究鋅空氣電池與鈉硫電池沒有取得實質(zhì)性進展,80年代在北京、天津、上海、洛陽、武漢、杭州、珠海等地研制電動汽車,12月成立了中壓電工技術(shù)學會電動車輛研究會,組織了多次學術(shù)交流,起了一定推動作用。我國己經(jīng)研制成多輛電動汽車,己列入國家計委“八五”項目的清華大學研制電動中型面包車,四川內(nèi)江“中山湖”電動微型汽車新寧汽車廠電動敞篷轎車,拖拉機研究所LY5010EC電動轎車,珠海偉達電動轎車,鄭州華聯(lián)機場電動牽引車及HL-42轎車投入市場,長江動力公司雙層電動大客車,中壓遠望總公司1990年開始與北京理工大學、國防科技大學、河北勝利客車廠及北京市電車公同聯(lián)合對電動汽車進行了調(diào)研與深入論證,關(guān)鍵技術(shù)大功率交流感應(yīng)電動機驅(qū)動控制部分從美國合作引進,1996年在首都北京亮相兩輛美觀大客車。發(fā)展電動汽車要從實際出發(fā),根據(jù)我國實際能達到行駛車速達50-70km/h,一次充電續(xù)駛里程達100km,單價為燃油汽車的兩倍左右。有五種車輛有廣泛的發(fā)展前途:城市大中型公共客車;機場擺渡車;城市公用事業(yè)服務(wù)車,如清潔車;中小型商業(yè)送貨車;游覽場所觀光游覽車,高爾夫球車等。也可以搞一些上述用途的豪華型客車。
2.電動汽車發(fā)展而臨的問題:
對于純電動汽車而言,其電池需要滿足較高的要求,包括高比能量、高比功率、快速充電和具有深度放電功能、循環(huán)和使用壽命長等“目前的電池一方而充電時間較長(在家充電需8-10小時),另一方面一次充電的行駛里程偏短,需要像建加油站那樣建設(shè)相當一批充電站,因此無法實現(xiàn)商業(yè)化量產(chǎn)。在各種車用電池中,鉛酸電池是比較成熟的技術(shù),具備較高的性價比和高倍率放電,是目前唯一能大批量生成的電動汽車用電池,但是其比能量、比功率和能量密度都比較低鎳鎘電池和鎳氫電池雖然性能好于鉛酸電池,但是其性價比不高,含重金屬,用完遺棄后對環(huán)境會造成嚴重污染。鋰離子動力電池的工作電壓和比能量較高,并且具有體積小、質(zhì)量輕、循環(huán)壽命長、自放電率低、無記憶效應(yīng)等優(yōu)點,不過目前的成本難以降低,而且由于鋰離子過于活潑,存在安全隱患,充電性能在低溫下大打折扣。同時成品車的成本也比較大。其它的問題有如黃魯成、顧威建在《電動汽車單于的未來》里而提到電動汽車面臨的問題有:A.整車系統(tǒng)集成進程緩慢;B.充電機車的普及遲緩;C.市場認識不足;D.成本過高;E.政府缺乏有力的指引支持??跌P林、李軍民在《電動汽車發(fā)展分析》里而提到電動汽車而臨的問題有:A續(xù)駛里程有限;B.蓄電池使用壽命太短;c.蓄電池尺寸和質(zhì)量制約;D.電動汽車價格昂貴;E.間接污染嚴重。在《發(fā)展電動汽車是解決中國汽車能源的理想途徑之一》里面提到電動汽車面臨的問題有:A.政府的政策支持;B.蓄電池技術(shù);C.基礎(chǔ)設(shè)施建設(shè);D.電機等重要部件技術(shù);E.電能的供應(yīng);F.市場的認可。
3.我國電動汽車產(chǎn)業(yè)未來發(fā)展:建立電動汽車技術(shù)創(chuàng)新平臺
目前我國電動汽車項目尚處于開發(fā)研制階段,還沒有形成生產(chǎn)規(guī)模,而對新一輪汽車產(chǎn)業(yè)結(jié)構(gòu)調(diào)整及技術(shù)升級的局而,我們的技術(shù)力量分散,難形成合力,無法實現(xiàn)新一代汽車的突破性創(chuàng)新。因此,要實現(xiàn)跨越式發(fā)展,只有建立汽車技術(shù)創(chuàng)新平臺,集成現(xiàn)有的汽車科技資源,以實現(xiàn)聯(lián)合攻關(guān),并形成良好的運作機制與相關(guān)科技創(chuàng)新平臺實現(xiàn)互動,才能實現(xiàn)我國電動汽車產(chǎn)業(yè)的持續(xù)發(fā)展“發(fā)達國家的電動汽車已經(jīng)取得了突破性的進展,正處于大規(guī)模產(chǎn)業(yè)化的邊緣,將引起一場規(guī)模龐大的汽車技術(shù)革命,這將對我國電動汽車企業(yè)造成極大的威脅。我國汽車企業(yè)的規(guī)模及市場規(guī)模還不足以支撐新一代電動汽車產(chǎn)品開發(fā)所需的技術(shù)基礎(chǔ)和成本支出,應(yīng)在技術(shù)創(chuàng)新平臺上促成“點”、“線”的集成,以尋求“面”的突破。因此,只有在政府的組織和重點支持下建立汽車技術(shù)創(chuàng)新平臺,聚集科技人才和科技成果,才能實現(xiàn)新一代電子汽車關(guān)謎技術(shù)和重點的突破。
主要參考文獻
[1]王望予.汽車設(shè)計[M].北京:機械工業(yè)出版社2004.8
[2]于志生.汽車理論[M].北京:機械工業(yè)出版社2006.8
[3]陳家瑞.汽車構(gòu)造[M].北京:機械工業(yè)出版社2005.1
[4]陳清泉,詹宜巨.21世紀的綠色交通工具——電動車(第一版)[M].北京:清華大學出版社.2000.1012103
[5]北京博信誠達信息咨詢中心研發(fā)部2009-2012年中國電動汽車行業(yè)深度研究報告電子版[J].SD2009501
[6] Mehrdad Ehsani, Yimin Gao, Ali Emadi. Modern electric hybrid electric and cell vehicles[M].CRC Press, 2009
[7]王剛,周榮.電動汽車充電技術(shù)研究[J].農(nóng)業(yè)裝備與車輛工程,2008,(6)
[8]徐性怡電動汽車用電機控制器的設(shè)計方法與實踐[J],2009,(6)
[9]姬芬竹,高峰電動汽車傳動系參數(shù)設(shè)計及動力性仿真[J].北京航空航天大學學報,2006
[10]趙云.電動汽車結(jié)構(gòu)布置及設(shè)設(shè).汽車電器,2006
[11]鄒立群.世界電動汽車發(fā)展綜述[J].電機與電器.2003.8
[12]劉磊.電動汽車蓄電池的建模與仿真研究.武漢理上大學碩士論文[D].2005:13~15
[13]李興虎.電動汽車概論[M].北京理工大學出版社,2005.8
[14]Chan C C. Chau KT. Modem electric vehicle technology. New York : Oxford University Press. 2001
[15]WU Hong—zing, Cheng, Shu-Kang, Cui Shu-Mei. Communication of Vehicle Management Unit in The Electric Vehicle [J].IEEE Transactions on Magnetics . 2005,41(1):514 ~ 517
[16]劉清虎,郭孔輝.動力參數(shù)的選擇對純電動汽車性能的影響[J].湖南大學學報(自然科學版)2003,30(3):62~64
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AUTOMATIC TRANSMISSION
The modern automatic transmission is by far , the most complicated mechanical component in today’s automobile . It is a type of transmission that sifts itself . A fluid coupling or torque converter is used instead of a manually operated clutch to connect the transmission to the engine .
There are two basic types of automatic transmission based on whether the vehicle is rear wheel drive or front wheel drive . On a rear wheel drive car , the transmission is usually mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position . A drive shaft connects the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheels . Power flow on this system is simple and straight forward going from the engine , through the torque converter , then trough the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear transmission .
On a front wheel drive car , the transmission is usually combined with the final drive to form what is called a transaxle . The engine on a front wheel drive car is usually mounted sideways in the car with the transaxle tucked under it on the side of the engine facing the rear of the car . Front axles are connected directly to the transaxle and provide power to front wheels . In this example , power floes from the engine , through the torque converter to a larger chain that sends the power through a 180 degree turn to the transmission that is along side the engine . From there , the power is routed through the transmission to the final drive where it is split and sent to the two front wheels through the drive axles .
There are a number of other arrangements including front drive vehicles where the engine is mounted front to back instead of sideways and there are other systems that drive all four wheels but the two systems described here are by far the most popular . A much less popular rear and is connected by a drive shaft to the torque converter which is still mounted on the engine . This system is found on the new Corvette and is used in order to balance the weight evenly between the front and rear wheels for improved performance and handling . Another rear drive system mounts everything , the engine , transmission and final drive in the rear . This rear engine arrangement is popular on the Porsche.
Automobile available more than a century, especially from the mass production of motor vehicles and the automotive industry since the development of large, Car has been the economic development of the world for mankind to enter the modern life and have had a tremendous impact on the immeasurable, The progress of human society has made indelible contributions to the great, epoch-making set off arevolution. From From the vehicle as a power plant using internal combustion engine to start, auto transmission has become an important component. Is Generation is widely used in automotive reciprocating piston internal combustion engine with a small size, light weight, reliable operation and the use of The advantages of convenience, but its torque and speed range of smaller changes, and complex condition requires the use of motor vehicles Traction and the speed can be considerable changes in the scope. Therefore, its performance and vehicle dynamics and economy of There are large inter-contradictions, which contradictions of modern automotive internal combustion engine by itself is insoluble. Because Here, in the automotive power train set up the transmission and main reducer in order to achieve the purpose of deceleration by moment. Speed The main function of performance: ⑴ change gear ratio of motor vehicles, and expand the wheel drive torque and rotational speed of the Fan Wai, in order to adapt to constantly changing driving cycle, while the engine in the most favorable conditions within the scope of work; ⑵ no change in the direction of engine rotation, under the premise of the realization of cars driving back; ⑶ the realization of the free, temporary Interruption of power transmission, in order to be able to start the engine, idling, etc.. Variable-speed drive transmission by the manipulation of institutions and agencies. Change the transmission ratio by way of transmission is divided into There are class-type, non-stage and multi-purpose three. Have class most widely used transmission. It uses gear drive, with a number of transmission ratio setting. Stepless transmission Continuously Variable Transmission (CVT) transmission ratio of a certain The framework of multi-level changes may be unlimited, there is a common type of power and torque (dynamic fluid-type) and so on. Continuously Variable Transmission Transmission development is the ultimate goal, because only it can make the most economical engine in working condition Can provide the best vehicle fuel economy and optimal power in order to provide the most comfortable By the feeling. Today's CVT is a typical representative of the CVT and IVT, however as a result of the reliability of Poor, non-durable materials and high cost issues, development is not very good. Comprehensive refers to transmission torque converter and the mechanical components have the level of transmission variable hydraulic mechanical Speed, the transmission ratio can be between the maximum and minimum range of a few discontinuous change for no class, but its Significantly lower transmission efficiency than the efficiency of gear drives. 2 By manipulation, transmission control type can be divided into mandatory, automatic and semi-automatic control to manipulate three - Species . Mandatory on the driver to manipulate the direct transmission gear shift control for the majority of motor vehicles used Also known as Manual Transmission Manual Transmission (MT). Automatic transmission control selection of the transmission ratio (transmission) is carried out automatically. Just add the driver to manipulate Speed pedal, you can control the speed, also known as Automatic Transmission Automatic Transmission (AT). It is According to the speed and load (throttle pedal travel) for two-parameter control, stall in accordance with the above two Parameters to automatically take-off and landing. AT and MT in common is that they are level transmission, but AT According to the speed of the speed shift automatically, you can eliminate the manual transmission "setback" of the shift feel. However, AT also have many drawbacks, such as body complex, mechanical efficiency is not high, high cost, reliability and control Sensitivity remains to be increasing . AMT (Automated Mechanical Transmission) is in the traditional dry clutch and manual transmission gear based on the transformation of form, mainly to change the part of the manual gearshift control. That is, the overall structure of the MT cases the same switch to electronically controlled automatic transmission to achieve. Semi-automatic control, there are two forms of transmission. A number of stalls is a common automatic control, and the remaining stalls manipulated by the driver; the other is pre-style, that is, pre-selected pilot stalls, the clutch pedal in the down or release the accelerator pedal, the for retirement or an electromagnetic device to shift the hydraulic device. In recent years, with advances in vehicle technology and road traffic density increased, the performance requirements of the transmission is also getting higher and higher. A large number of automotive engineers in improving the performance of automobile transmission study a great deal of effort devoted to the rapid transmission of technology development, such as AT, AMT, DCT, CVT and the emergence of IVT.
The modern automatic transmission consists of many components and systems that designed to work together in a symphony of planetary gear sets , the hydraulic system, seals and gaskets , the torque converter , the governor and the modulator or throttle cable and computer controls that has evolved over the years into what many mechanical inclined individuals consider to be an art from . Here try to used simple , generic explanation where possible to describe these systems .
1)Planetary gear sets
Automatic transmission contain many gears in various combinations . In a manual transmission , gears slide along shafts as you move the shift lever from one position to another , engaging various sizes gears as required in order to provide the correct gear ratio . In an automatic transmission , how ever , the gears are never physically moved and are always engaged to the same gears . This is accomplished through the use of planetary gear sets .
The basic planetary gear set consists of a sun gear , a ring and two or more planet gears , all remaining in constant mesh . The planet gears are connected to each other through a common carrier which allows the gears to spin on shafts called “pinions” which are attached to the carrier .
One example of a way that this system can be used is by connecting the ring gear to the input shaft coming from the engine , connecting the planet carrier to the output shaft , and locking the sun gear so that it can’t move . In this scenario , when we turn the ring gear , the planets will “walk” along the sun gear ( which is held stationary ) causing the planet carrier to turn the output shaft in the same direction as the input shaft but at a slower speed causing gear reduction ( similar to a car in first gear ) .
If we unlock the sun gear and lock any two elements together , this will cause all three elements to turn at the same speed so that to output shaft will turn at the same rate of speed as the input shaft . This is like a car that is third or high gear . Another way we can use a planetary gear set is by locking the planet carrier from moving , then applying power to the ring gear which will cause the sun gear to turn in opposite direction giving us reverse gear .
The illustration in Figure shows how the simple system described above would look in an actual transmission . The input shaft is connected to the ring gear , the output shaft is connected to the planet carrier which is also connected to a “Multi-disk” clutch pack . The sun gear is connected to drum which is also connected to the other half of the clutch pack . Surrounding the outside of the drum is a band that can be tightened around the drum when required to prevent the drum with the attached sun gear from turning .
The clutch pack is used , in this instance , to lock the planet carrier with the sun gear forcing both to turn at the same speed . If both the clutch pack and the band were released , the system would be in neutral . Turning the input shaft would turn the planet gears against the sun gear , but since noting is holding the sun gear , it will just spin free and have no effect on the output shaft . To place the unit in first gear , the band is applied to hold the sun gear from moving . To shift from first to high gear , the band is released and the clutch is applied causing the output shaft to turn at the same speed as the input shaft .
Many more combinations are possible using two or more planetary sets connected in various way to provide the different forward speeds and reverse that are found in modern automatic transmission .
2)Clutch pack
A clutch pack consists of alternating disks that fit inside a clutch drum . Half of the disks are steel and have splines that fit into groves on the inside of the drum . The other half have a friction material bonded to their surface and have splines on the inside edge that fit groves on the outer surface of the adjoining hub . There is a piston inside the drum that is activated by oil pressure at the appropriate time to squeeze the clutch pack together so that the two components become locked and turn as one .
3)One-way Clutch
A one-way clutch ( also known as a “sprag” clutch ) is a device that will allow a component such as ring gear to turn freely in one direction but not in the other . This effect is just like that bicycle , where the pedals will turn the wheel when pedaling forward , but will spin free when pedaling backward .
A common place where a one-way clutch is used is in first gear when the shifter is in the drive position . When you begin to accelerate from a stop , the transmission starts out in first gear . But have you ever noticed what happens if you release the gas while it is still in first gear ? The vehicle continues to coast as if you were in neutral . Now , shift into Low gear instead of Drive . When you let go of the gas in this case , you will feel the engine slow you down just like a standard shift car . The reason for this is that in Drive , one-way clutch is used whereas in Low , a clutch pack or a band is used .
4)Torque Converter
On automatic transmission , the torque converter takes the place of the clutch found on standard shift vehicles . It is there to allow the engine to continue running when the vehicle comes to a stop . The principle behind a torque converter is like taking a fan that is plugged into the wall and blowing air into another fan which is unplugged . If you grab the blade on the unplugged fan , you are able to hold it from turning but as soon as you let go , it will begin to speed up until it comes close to speed of the powered fan . The difference with a torque converter is that instead of using air it used oil or transmission fluid , to be more precise .
A torque converter is a lager doughnut shaped device that is mounted between the engine and the transmission . It consists of three internal elements that work together to transmit power to the transmission . The three elements of the torque converter are the pump , the Turbine , and the Stator . The pump is mounted directly to the torque housing which in turn is bolted directly to the engine’s crankshaft and turns at engine speed . The turbine is inside the housing and is connected directly to the input shaft of the transmission providing power to move the vehicle . The stator is mounted to a one-way clutch so that it can spin freely in one direction but not in the other . Each of the three elements has fins mounted in them to precisely direct the flow of oil through the converter .
With the engine running , transmission fluid is pulled into the pump section and is pushed outward by centrifugal force until it reaches the turbine section which stars it running . The fluid continues in a circular motion back towards the center of the turbine where it enters the stator . If the turbine is moving considerably slower than the pump , the fluid will make contact with the front of the stator fins which push the stator into the one way clutch and prevent it from turning . With the stator stopped , the fluid is directed by the stator fins to re-enter the pump at a “help” angle providing a torque increase . As the speed of the turbine catches up with the pump , the fluid starts hitting the stator blades on the back-side causing the stator to turn in the same direction as the pump and turbine . As the speed increase , all three elements begin to turn at approximately the same speed . Sine the ‘80s , in order to improve fuel economy , torque converters have been equipped with a lockup clutch which locks the turbine to the pump as the vehicle reaches approximately 40-50 mph . This lockup is controlled by computer and usually won’t engage unless the transmission is in 3rd or 4th gear .
5)Hydraulic System
The hydraulic system is a complex maze of passage and tubes that sends that sends transmission fluid and under pressure to all parts of the transmission and torque converter and . Transmission fluid serves a number of purpose including : shift control ,general lubrication and transmission cooling . Unlike the engine ,which uses oil primary for lubrication ,every aspect of a transmission ‘s function is dependant on a constant supply of fluid is send pressure . In order to keep the transmission at normal operating temperature , a portion of the fluid is send to through one of two steel tubes to a special chamber that is submerged in anti-freeze in the radiator . Fluid passing through this chamber is cooled and then returned to the transmission through the other steel tube . A typical transmission has an avenge of ten quarts of fluid between the transmission , torque converter , and cooler tank , In fact , most of the components of a transmission are constantly submerged in fluid including the clutch packs and bands . The friction surfaces on these parts are designed to operate properly only when they are submerged in oil .
6)Oil Pump
The transmission oil pump ( not to confused with the pump element inside the torque converter ) is responsible for producing all the oil pressure that is required in the transmission . The oil pump is mounted to front of the transmission case and is directly connected to a flange on the engine crankshaft , the pump will produce pressure whenever the engine is running as there is a sufficient amount of transmission fluid available . The oil enters the pump through a filter that is located at bottom of the transmission oil pan and travels up a pickup tube directly to the oil pump . The oil is then sent , under pressure to the pressure regulator , the valve body and the rest of the components , as required .
7)Valve Body
The valve body is the control center of the automatic transmission . It contains a maze of channels and passages that direct hydraulic fluid to the numerous valves which when activate the appropriate clutch pack of band servo to smoothly shift to the appropriate gear for each driving situation . Each of the many valves in the valve body has a specific purpose and is named for that function . For example the 2-3 shift valve activates the 2nd gear up-shift or the 3-2 shift timing valve which determines when a downshift should occur .
The most important valve and the one that you have direct control over is the manual valve. The manual valve is directly connected to the gear shift handle and covers and uncovers various passages depending on what position the gear shift is paced in . When you place the gear shift in Drive , for instance , the manual valve directs fluid to the clutch pack ( s ) that activates 1st gear . It also sets up to monitor vehicle speed and throttle position so that it can determine the optimal time and the force for the 1-2 shift . On computer controlled transmission , you will also have electrical solenoids that are mounted in the valve body to direct fluid to the appropriate clutch packs or bands under computer control to more precisely control shift points .
8)Seals and Gaskets
An automatic transmission has many seals and gaskets to control the flow of hydraulic fluid and to keep it from leaking out . There are two main external seals : the front seal and the rear seal . The front seal seals the point where the torque converter mounts to the transmission case . This seal allows fluid to freely move from the converter to the transmission but keeps the fluid from leaking out . The rear seal keeps fluid from leaking past the output shaft .
A seal is usually made of rubber ( similar to the rubber in a windshield wiper blade ) and is used to keep oil from leaking past a moving part such as a spinning shaft . In some cases , the rubber is assisted by a spring that holds he rubber in close contact with the spinning shaft .
A gasket is a type of seal used to seal two stationary parts that are fasted together . Some common gasket materials are : paper , cork , rubber , silicone and soft metal .
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