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車輛與動(dòng)力工程學(xué)院畢業(yè)設(shè)計(jì)說明書 I 3 噸柴油動(dòng)力貨車設(shè)計(jì)（后驅(qū)動(dòng)橋與后懸架設(shè)計(jì)） 摘要 驅(qū)動(dòng)橋是將傳動(dòng)軸傳來的扭矩進(jìn)行減速增扭，并改變其扭矩的方向，再分配 給左右車輪，并使左右車輪具有差速作用，以保證內(nèi)外車輪以不同的轉(zhuǎn)速轉(zhuǎn)向。 懸架是現(xiàn)代汽車上的重要總成之一,它用來感知不同地面給車架的不同程度的， 方向上的力，并利用機(jī)構(gòu)中的彈簧來減小路面的崎嶇不平對(duì)乘客乘坐舒適感的影 響。 這次設(shè)計(jì)從驅(qū)動(dòng)橋開始，首先是對(duì)驅(qū)動(dòng)橋的總體認(rèn)識(shí)，根據(jù)設(shè)計(jì)要求對(duì)驅(qū)動(dòng) 橋的形式進(jìn)行選擇。然后是對(duì)主減速器的設(shè)計(jì)計(jì)算，包括對(duì)主減速器的概述，形 式的選擇，主減速器齒輪參數(shù)的設(shè)計(jì)計(jì)算，主減速比及載荷的確定，差速器的選 擇，半軸和行星齒輪的參數(shù)計(jì)算，半軸的計(jì)算，選擇以及對(duì)上述各個(gè)部分的強(qiáng)度 校核計(jì)算。對(duì)懸架的設(shè)計(jì)參考了多種車型，選擇鋼板彈簧非獨(dú)立懸架，內(nèi)容包括 懸架形式的選擇，鋼板和減震器的計(jì)算等。 懸架的作用是傳遞車架（承載式車身）和車橋之間一切力和力矩。這次設(shè)計(jì) 采用非獨(dú)立懸架。 設(shè)計(jì)的重點(diǎn)是對(duì)主減速器的齒輪進(jìn)行設(shè)計(jì)和計(jì)算。懸架方面，鋼板彈簧的選 擇和剛度校核是關(guān)鍵。對(duì)于各個(gè)軸和齒輪的接觸和彎曲強(qiáng)度校核都符合要求。 關(guān)鍵詞：驅(qū)動(dòng)橋，主減速器，半軸，鋼板彈簧 車輛與動(dòng)力工程學(xué)院畢業(yè)設(shè)計(jì)說明書 II 3T DIESEL FUEL POWER TRUCK DESIGN（REAR DRIVING AXLE AND REAR SUSPENSIONASSEMBLY) ABSTRACT Driving axle works that transmission shaft brought over torque proceed deceleration speed increased，combine transfer his tensional heading，reassign given about left and right wheel. combine gotten about possess differential acting ， withal guarantee wheel inside and outside and withal different rotation rate turn，The suspension system is the important part of the morden automotive, the suspension system feel much power of the frame from the road surface, sping in the system absorb the shocks of all kinds of the road surface, so that passengers have a comfortable ride. The design starts from the live axle ，first I know about type， It joins up handgrip carriage and axletree elastically. primary mission yes transfer action at wheel and carriage of compartment wholeness force and moment；relax pavement hand down to carriage shock load， attenuation resulting bearing systemic vibrate，guaranee garage gotten smoothness；guarantee wheel at pavement dissatisfaction and load fluctuation hour in the right would motility， The function of the suspension transfers all of force and moment between the frame ( bearing the weight of the body )and the axletree. This design adhibits the disindependencing suspension. The key of the design designs and calculate to gear wheel of the main reducing gear， The crux is the way of rear suspension,siderography selecting and rigidity.osculation intension Structure simplicity, usability best, adjust service easiness. KEY WORDS: driving axle，main reducing gear, semi axis, plate spring 車輛與動(dòng)力工程學(xué)院畢業(yè)設(shè)計(jì)說明書 III 符號(hào)說明 rr: 車輪的滾動(dòng)半徑 np: 最大功率時(shí)發(fā)動(dòng)機(jī)的轉(zhuǎn)速 vamax: 最高車速 igH: 變速器最高檔傳動(dòng)比 Temax: 發(fā)動(dòng)機(jī)最大轉(zhuǎn)矩 N: 驅(qū)動(dòng)橋數(shù)目 iTL: 由發(fā)動(dòng)機(jī)至所計(jì)算的主減速器從動(dòng)齒輪之間的傳系最檔傳動(dòng)比 T：上述傳動(dòng)部分傳動(dòng)效率 K0：離合器產(chǎn)生沖擊載荷時(shí)超載系數(shù) G2: 滿載時(shí)一個(gè)驅(qū)動(dòng)輪上的靜載荷系數(shù) : 輪胎與路面間的附著系數(shù) rr: 車輪的滾動(dòng)半徑 lB : 所計(jì)算的主減速器從動(dòng)齒輪到驅(qū)動(dòng)車輪之間的傳動(dòng)效率 ilB : 所計(jì)算的主減速器從動(dòng)齒輪到驅(qū)動(dòng)車輪之間的傳動(dòng)比 p：單位齒長上的圓周力 N/mm ig：變速器檔傳動(dòng)比 d1：主動(dòng)齒輪節(jié)圓直徑 F：動(dòng)齒輪的齒面寬 : 半軸的扭轉(zhuǎn)應(yīng)力 T ：半軸的計(jì)算轉(zhuǎn)矩 d：半軸桿部直徑 K ：超載系數(shù) Ks：尺寸系數(shù)，反映材料性質(zhì)的不均勻性，與齒輪尺寸及熱處理等有關(guān)。 Km：載荷分配系數(shù) Kv： 質(zhì) 量 系 數(shù) ， 對(duì) 于 汽 車 驅(qū) 動(dòng) 橋 齒 輪 ， 當(dāng) 齒 輪 接 觸 良 好 、 周 節(jié) 及 徑 向 跳 動(dòng) 精 度 高 時(shí) 車輛與動(dòng)力工程學(xué)院畢業(yè)設(shè)計(jì)說明書 IV 目 錄 第一章 前言............................................1 第二章 驅(qū)動(dòng)橋結(jié)構(gòu)方案分析..............................2 2.1 驅(qū)動(dòng)橋概述......................................2 2.2 驅(qū)動(dòng)橋形式及選擇................................3 第三章 主減速器設(shè)計(jì).....................................4 3.1 主減速器結(jié)構(gòu)方案分析............................4 3.2 主減速比及計(jì)算載荷的確定.......................4 3.2.1 主減速比 的確定............................40 3.2.2 齒輪計(jì)算載荷的確定... .....................4 3.3 主減速器齒輪主要參數(shù)計(jì)算........................5 3.3.1 主、從動(dòng)齒輪齒數(shù)的選擇..................6 3.3.2 從動(dòng)齒輪節(jié)圓直徑及端面模數(shù)的選擇...........6 3.3.3 齒面寬的選擇 ...........................7 3.3.4 雙曲面齒輪的偏移距.....................7 3.3.5 螺旋角的選擇............................7 3.3.6 圓弧齒雙曲面齒輪的幾何尺寸設(shè)計(jì)..........8 3.4 主減速器齒輪強(qiáng)度計(jì)算.........................18 3.4.1 單位齒上的圓周力..........................18 3.4.2 齒輪彎曲強(qiáng)度計(jì)算..........................19 3.4.3 齒輪接觸強(qiáng)度計(jì)算..........................20 3.5 主減速器的材料和熱處理......................21 3.6 主減速器錐齒輪軸承的載荷計(jì)算...................22 3.6.1 主減速器主動(dòng)錐齒輪上的當(dāng)量轉(zhuǎn)矩 的計(jì)算...221dT 3.6.2 主減速器主動(dòng)錐齒輪齒面寬中點(diǎn)處圓周力計(jì)算.22 3.6.3 雙曲面齒輪的軸向力與徑向力的計(jì)算........22 3.6.4 懸臂式支承主動(dòng)錐齒輪的軸承徑向載荷的確定.23 3.6.5 主減速器從動(dòng)錐齒輪的軸承計(jì)算.............25 第四章 差速器設(shè)計(jì)......................................27 4.1 差速器結(jié)構(gòu)方案分析...........................27 車輛與動(dòng)力工程學(xué)院畢業(yè)設(shè)計(jì)說明書 V 4.2 差速器齒輪主要參數(shù)計(jì)算.......................28 4.3 差速器齒輪強(qiáng)度計(jì)算...........................31 第五章 半軸及橋殼設(shè)計(jì)..................................33 5.1 半軸的設(shè)計(jì)計(jì)算. ................................33 5.1.1 半軸的形式.................................33 5.1.2 半軸參數(shù)計(jì)算...............................33 5.1.3 半軸的強(qiáng)度計(jì)算.............................30 5.2 半軸的結(jié)構(gòu)、材料與熱處理........................35 5.3 橋殼的設(shè)計(jì)計(jì)算.................................35 5.3.1 橋殼的設(shè)計(jì).................................35 5.3.2 橋殼強(qiáng)度計(jì)算...............................36 第六章 后懸架設(shè)計(jì)......................................33 6.1 后懸架概述.....................................33 6.2 后懸架的設(shè)計(jì)計(jì)算...............................35 6.2.1 懸架已知參數(shù)...............................39 6.2.2 懸架主要參數(shù)的確定.........................40 6.2.3 彈性元件的設(shè)計(jì)計(jì)算.........................40 6.2.4 后鋼板彈簧的計(jì)算.......................43 第七章 結(jié)論...........................................49 參考文獻(xiàn)...............................................50 致謝...................................................51 外文資料譯文
燃料汽車電子設(shè)備
隨著油價(jià)的不斷上漲，汽車制造商們正在重新設(shè)計(jì)發(fā)動(dòng)機(jī)管理系統(tǒng)，以適應(yīng)燃料中乙醇用量不斷增加的趨勢(shì)。
世界原油產(chǎn)量預(yù)計(jì)將在2010－2020年之間達(dá)到頂峰，期間，原油的消耗量將比新探明儲(chǔ)量更重要，原油價(jià)格也將會(huì)不停的上漲，交通業(yè)是耗油大戶，隨著油價(jià)的上漲，汽車必須提高燃油利用率。
汽車同時(shí)也是最大的污染源，在法規(guī)的約束下，交通運(yùn)輸所帶來的污染已經(jīng)得到了有效地改善，特別是鉛和一氧化碳的排放量明顯降低了。然而，一些長期的污染問題仍待解決，特別是以二氧化碳為代表的溫室氣體排放。
為了在競爭中生存，汽車制造商們正在研究能降低油耗或減少廢氣排放的新技術(shù)和代用燃料，作為一種代用燃料，乙醇憑借其靈活的使用方式，越來越多的受到青睞。駕駛員可以在標(biāo)準(zhǔn)的汽油和乙醇之間靈活的選擇。
“發(fā)動(dòng)機(jī)管理系統(tǒng)對(duì)于這種柔性燃料系統(tǒng)來說是必不可少的?！狈▏?yīng)商法雷奧稱，“改系統(tǒng)可以控制扭矩、輔助系統(tǒng)、診斷故障、更重要的是，他能控制廢氣排放?！?
扭矩控制功能可根據(jù)駕駛員需要的操縱性和加速能力調(diào)控發(fā)動(dòng)機(jī)的輸出扭矩、發(fā)動(dòng)機(jī)扭矩控制功能還可以和其他一些功能，如牽引力控制、巡航控制、變速器和制動(dòng)器等相互配合。
尾氣排放主要分為3類：排氣管排放、加油時(shí)產(chǎn)生的排放和蒸發(fā)性排放，要解決為期排放所帶來的問題，關(guān)鍵是要符合尾氣排放標(biāo)準(zhǔn)，同時(shí)盡量降低油耗。這兩點(diǎn)可以通過專用后處理裝置，如催化轉(zhuǎn)換器、傳感器和機(jī)電執(zhí)行機(jī)構(gòu)來實(shí)現(xiàn)。
發(fā)動(dòng)機(jī)管理系統(tǒng)控制扭矩和排放的方式很復(fù)雜，進(jìn)入發(fā)動(dòng)機(jī)的空氣和再循環(huán)廢氣通過專用的傳感器和執(zhí)行機(jī)構(gòu)實(shí)現(xiàn)精確的定量控制，首先噴入適量的燃油，以實(shí)現(xiàn)最能發(fā)揮催化劑效率的最佳空\燃比，接著適時(shí)點(diǎn)燃混合氣，三元催化會(huì)最終使廢氣排放保持在可接受的水平上。
所有這些功能需要通過數(shù)據(jù)總線和導(dǎo)線的連接與其它電子裝置相互配合。通過這些裝置發(fā)回的反饋信息，發(fā)動(dòng)機(jī)管理系統(tǒng)可以屏蔽無關(guān)的干擾和變化。
提高燃油利用率和減少溫室氣體排放可通過采用發(fā)動(dòng)機(jī)技術(shù)或使用不同的燃料來實(shí)現(xiàn)。至于哪種方法更好，這要取決于成本、市場(chǎng)接受度以及政治和財(cái)政上的刺激等因素。
例如，使用E85燃料，即含85％乙醇和15％汽油的混合燃料的汽車，其排放量只有單純使用汽油時(shí)的79％，乙醇之所以成為廣受歡迎的代用燃料，主要是因?yàn)樗暮剂勘绕蜕?，所以燃燒時(shí)產(chǎn)生的廢氣也相對(duì)較少。
與使用汽油的車相比，大部分使用酒精的車一氧化碳和二氧化碳排放量更低、烷烴或非烷烴碳?xì)渑欧帕肯嗟然蚋?，使用乙醇和汽油的汽車所產(chǎn)生的氮氧化物排放量大致相同，因?yàn)橐掖既剂系母邠]發(fā)性成分含量比汽油低，所以蒸發(fā)性排放量也較低。
此外，乙醇可以用農(nóng)作物來生產(chǎn)，因此是一種可再生燃料，生物乙醇實(shí)際上不產(chǎn)生任何來自化石的二氧化碳，也就是說，二氧化碳的凈增加值為零 。
減少汽車排放量的潛力是巨大的，但如果完全依賴生物燃料，則需要大量的種植面積，因此在今后的一段時(shí)間里，乙醇的市場(chǎng)占有率與原油相比仍將十分有限，如果汽車能在兩種燃料之間靈活選擇，那么用乙醇做燃料仍不失為一種緩解石油危機(jī)的有效方法。
與傳統(tǒng)汽車發(fā)動(dòng)機(jī)相比，裝有柔性燃料發(fā)動(dòng)機(jī)管理系統(tǒng)的發(fā)動(dòng)機(jī)在不增加成本的情況下，可以在普通無鉛汽油和含酒精0到100％的混合燃料之間任意轉(zhuǎn)換，正是因其幾乎不需要增加額外成本，該技術(shù)在農(nóng)業(yè)資源富庶的國家尤其受歡迎。
然而，對(duì)原有發(fā)動(dòng)機(jī)進(jìn)行一些改裝還是必要的。汽油發(fā)動(dòng)機(jī)上使用的某些材料和酒精是完全不相容的?！叭剂系母g性和揮發(fā)性是對(duì)零部件影響最大的兩個(gè)因素，”法雷奧公司稱，“因此需要對(duì)油泵、燃油管路、油箱和噴油器的材料和設(shè)計(jì)進(jìn)行更改?！?
但是并沒有必要為乙醇特制熱導(dǎo)傳感器。乙醇的理論空/燃比與汽油相差很大，例如E100為9:1,E85為10:1,3而汽油則為14.7:1，因此，可以用汽油機(jī)上已有的標(biāo)準(zhǔn)氧化傳感器來確定酒精和汽油的含量。
盡管從加油泵中流出的混合燃料的酒精含量是一定的，但油箱里的酒精含量可能會(huì)不一樣，因?yàn)榧尤氲娜剂峡赡軙?huì)和油箱中原來剩余的燃料混合在一起，這就需要發(fā)動(dòng)機(jī)管理系統(tǒng)根據(jù)汽車的實(shí)際情況進(jìn)行調(diào)整，以保證最佳的運(yùn)轉(zhuǎn)效果。
相同體積的乙醇所含的能量比汽油大約低30％，燃料消耗也相應(yīng)的比汽油機(jī)高30％，為了解決效率降低的問題，汽車制造商們將油箱的容積相應(yīng)增大，這樣汽車的行駛里程就不會(huì)因此降低，噴油器的流量范圍也必須相應(yīng)的增大。
由于乙醇中含有的高揮發(fā)性物質(zhì)比汽油少，因此可能會(huì)因發(fā)冷起動(dòng)問題，解決這一問題有兩個(gè)方法：在美國和瑞典，混合燃料中至少含有一定量的汽油，冬季的汽油含量可高達(dá)30％，在瑞典，冬天常常需要在－10℃的低溫下起動(dòng)，為此，車輛都備有一種電熱裝置為汽車保溫。
在巴西，人們用純酒精作燃料，不過在車上要另加一個(gè)小型的備用汽油油箱，并且專門為冷起動(dòng)增加一套燃油管。同時(shí)也可以通過改進(jìn)啟動(dòng)器來增加起動(dòng)時(shí)的轉(zhuǎn)速。
巴西產(chǎn)的柔性燃料汽車上，發(fā)動(dòng)機(jī)管理系統(tǒng)必須控制來自冷起動(dòng)油箱的輸入信號(hào)，并且在該油箱油量過低時(shí)能夠察覺；系統(tǒng)的輸出信號(hào)必須能通過電控汽油泵繼電器和冷起動(dòng)噴油電磁閥，控制冷起動(dòng)的供油量。
這種車上還可以選裝顯示設(shè)備，包括顯示所用燃料和冷啟動(dòng)油箱位過低的指示器。這些功能用標(biāo)準(zhǔn)汽油機(jī)ECU進(jìn)行重新設(shè)計(jì)。
在寒冷天氣里，發(fā)動(dòng)機(jī)管理系統(tǒng)在啟動(dòng)專用的電控泵和電磁閥的同時(shí)，用汽油進(jìn)行“全組壁濕預(yù)噴”。一旦發(fā)動(dòng)機(jī)達(dá)到足夠快的轉(zhuǎn)速，噴油器就會(huì)開始噴射乙醇。因此，汽油噴射在幾秒鐘之內(nèi)就會(huì)停止。
發(fā)動(dòng)機(jī)管理系統(tǒng)是怎么知道燃油的混合比的？不是靠不斷的測(cè)量混合氣的濃度，而是通過標(biāo)準(zhǔn)的上游氧傳感器來確定酒精和汽油的量。該傳感器可測(cè)出實(shí)現(xiàn)最佳催化率所需的空然比和實(shí)際空燃比的差。
“微小的誤差可通過用于噴油正時(shí)的‘A反饋’校正法直接消除，誤差很大時(shí)，則說明燃料的性質(zhì)發(fā)生了改變。”法雷奧公司稱。“然后，發(fā)動(dòng)機(jī)管理系統(tǒng)會(huì)重新對(duì)空然比進(jìn)行估算，并根據(jù)實(shí)驗(yàn)所得的空/ 燃比和汽油/乙醇比之間的對(duì)應(yīng)關(guān)系，將其換算為汽油和乙醇的混合比?！?
為了增強(qiáng)可靠性，一有跡象表明燃料很可能發(fā)生了改變，發(fā)動(dòng)機(jī)管理系統(tǒng)就會(huì)對(duì)酒精濃度進(jìn)行估算。估算的時(shí)候采用關(guān)于主油箱油位的信息，如果發(fā)動(dòng)機(jī)管理系統(tǒng)能收到這樣的信息的話。
將發(fā)動(dòng)機(jī)所需的扭矩?fù)Q算為發(fā)動(dòng)機(jī)管理系統(tǒng)所需的空氣、燃料用量和點(diǎn)火時(shí)間時(shí)，需要考慮實(shí)際參數(shù)的變化，如理論空燃比、熱值和燃燒效率等?！皩?duì)于混和燃料，發(fā)動(dòng)機(jī)管理系統(tǒng)的各個(gè)參數(shù)和各種行為是通過將估算的乙醇/汽油比作為插值參數(shù)而求出的，”法雷奧公司稱，在計(jì)算噴油量和點(diǎn)火提前指時(shí)用的是同一參數(shù)。
進(jìn)氣量也會(huì)發(fā)生變化，汽油和乙醇的蒸發(fā)潛熱值相差很大，簡單的說，乙醇會(huì)使吸入的空氣因冷卻而密度增加。進(jìn)入氣缸內(nèi)的空氣質(zhì)量隨之增大。為此，校準(zhǔn)進(jìn)氣量時(shí)就必須按100%乙醇和100%汽油兩種情況進(jìn)行。
“據(jù)我們估計(jì)，幾年內(nèi)大部分歐洲和美國汽車都會(huì)在燃油中加入乙醇?！狈ɡ讑W公司表示，“E85燃料是否會(huì)成為標(biāo)準(zhǔn)還很難說，不過我們以為此作好準(zhǔn)備。”
4
fuel electronics
As oil gets more expensive, carmakers are looking at engine management systems that can cope with increasing levels of ethanol.
Oil production could peak between 2010 and 2020.When it happens ,oil consumption will become more important than new discoveries ;and crude oil prices will rise and rise .Transport is the dominant sector in terms of oil use and motor vehicles will have to become more fuel-efficient.
Vehicles are the largest source of pollution. Regulations have addressed the problem for transportation and real improvements have been achieved ,particularly in lead and carbon monoxide levels .But some long-term emissions have not been considered .This is particularly eve case for greenhouse gas emissions ;carbon dioxide in particular.
To protect their livelihoods ,carmakers are investigating technologies and alternative fuels that either reduce oil consumption or cut emissions .Ethanol is starting to become more attractive as it can be used flexibly .The driver can run on standard gasoline or on
The engine management system is an essential part of such systems’ success ,says French Tier One supplier Valeo :“They control
Torque, ancillary systems ,diagnose servicing issues and ,most importantly ,emissions.”
Torque control features deliver engine responses with levels of drivability and acceleration in agreement with users’ requests .Engine torque control also co-prorates functions such as traction control, cruise control, transmissions and brakes.
Emissions break down into three main areas: those from the exhaust tailpipe; refueling losses and evaporative emissions .The issue is to comply with emission regulations and minimize fuel consumption .This is achieved through dedicated after-treatment components such as catalytic converters, sensors and electro-mechanical actuators.
The way the engine management system controls torque and emission is complex .The quantities of air and recycled exhaust gases entering the engine are precisely managed with dedicated sensors and actuators .The right air/fuel mix for the catalyst to work properly .The mix has to ignite at the right time .The three-way catalyst then has to keep final pollutant emissions at acceptable levels.
All these functions need to cooperate with other electronic units through data buses and eventually wired connections .Feedback from them allows the system to ignore any irrelevant disturbances and variations.
Fuel efficient driving and reduction of greenhouse gas emissions can be achieved by using engine technologies or different fuels .Which prevails will depend on cost ,market acceptance ,and political and fiscal incentives.
A vehicle fuelled with E85 fuel ,which contains 85 percent ethanol and 15 percent gasoline ,produces just 79percent of the emissions produced by pure gasoline .The interest in ethanol as an alternative fuel comes mainly from its clean burning qualities .Ethanol contains less carbon than gasoline.
Compared with gasoline, most ethanol cars produce lower carbon monoxide and carbon dioxide emissions and the same or lower levels of hydrocarbon and non-methane hydrocarbon hydro carton emissions Oxides of nitrogen emissions are about the same for ethanol and gasoline vehicles.
Ethanol fuel has fewer highly volatile components than gasoline and so has emissions.
Moreover it can be produced from crops and so qualifies renewable fuel .Bio-ethanol produces no fossil carbon dioxide because the plants used to make ethanol take CO2 out of the air in order to grow . There is a net increase of zero.
There is no need, however, to fit a specific ethanol conductivity sensor .The stoichometric air-fuel ratio of ethanol is very different to gasoline .For E100 it is 9:1, for E85 is it 10:1,for gasoline it is 14.7:1.Because of this ,it is possible to recognize the amount of ethanol and gasoline by using the standard oxygen sensor already found in gasoline architectures.
Although the ethanol content of the blend at a refueling pump is specified ,the content of the vehicle tanks may be different because it may mix with any fuel already in the vehicle’ stank .It is the job of the engine management system to make the adjustments the vehicle needs to operate optimally.
The energetic content of ethanol is around 30 percent less than the same volume of gasoline .Fuel consumption is potentially increased in the same proportion .To deal with the decline in fuel efficiency, carmakers install larger fuel tanks, so the vehicle’s range is not compromised .Injectors’ flow ranges have to be increased too.
Ethanol has fewer highly volatile components than gasoline ,so Cole starting problems may occur .To solve this issue two kinds of solutions ate used ;In the US and Sweden ,a fuel with a minimal amount of gasoline is used ,the amount of gasoline can be as high as 30 percent in the winter .In Sweden ,where cold starts at -10℃ are common in the winter ,the vehicle is plugged in to an electric source to keep it warm.
In Brazil, pure hydrated ethanol is used but with a small additional gasoline reserve tank and fuel line that is used only for cold starts .Starters can also be modified to increase the cranking speed.
In Brazilian flex-fuel vehicle architectures, the engine management system must manage inputs from the cold start tank, recognizing when fuel is low .Its outputs must manage gasoline supply for cold start via an electric gasoline pump relay and a cold-start injection solenoid valve.
Optional driver display information includes indicators to show the type of fuel in use and when the cold start tank is low .These features require hardware that is usually available as spares on standard gasoline ECUs .so no specific ECU has to be designed.
In cold weather ,the engine management system orders a wall-wetting ,full-group pre-injection is performed using gasoline ,by simultaneously activating the dedicated electric pump and the solenoid valve .As soon as the engine speed is high enough the injectors inject the ethanol .Gasoline injection is then phased out within a few seconds.
How does it know that the fuel blend is? Not by constantly measuring the mix .A standard upstream oxygen sensor recognizes the amount of ethanol and gasoline. This sensor measures the difference between the air/fuel ratio required for optimal catalyst efficiency and those effectively achieved.
“Slight errors are directly cancelled with the lambda feedback correction performed on injection timing, while large ones are arreibuted to changes in fuel characteristic.” says Valeo .The new air/fuel ratio is then estimated and translated into gasoline ethanol ratio .This translation is gassed on the experimental relationship between air/fuel and gasoline/ethanol ratios.
To improve robustness, estimating the ethanol ratio is triggered as far as possible by information indicating that it is likely that there has been a fuel change. When available, information on the main tank level is used.
The translation of torque requests into engine management requests for the air, fuel and ignition has to take into account differences in physical parameters such as the stoichometric ratio, calorific power and combustion efficiency. For blend fuels, engine management parameters and behaviors are obtained by using the estimated ethanol/gasoline ratio as an interpolating parameter. Says Valeo .The same is used to calculate injection masses and spark advance values.
Air loads differ too .There are significant differences between gasoline and ethanol’s latent heat vaporization. Roughly speaking ,the ethanol cools down the intake air and thus increases its density .The air mass admitted into the cylinders is higher as a result .Because of this ,air load calibrations have to cater for both 100 percent ethanol and 100 percent gasoline.
“We expect ethanol to be blended with gasoline in most European and US fuel in the next few years,” sys Valeo. “Whether E85 will become the rule is more difficult to say, but we are ready for it.”