畢業(yè)設計（論文）附件資料課題名稱 轎車驅動橋設計 系 別專 業(yè)班 級學 號姓 名指導教師畢業(yè)設計（論文）方案論證課題名稱 轎車驅動橋設計 系 別專 業(yè)班 級學 號姓 名指導教師 2011 年 5 月1目 錄原文： .1譯文 .6第一章 方案論證 .91.1 主減速器結構方案分析 .91.2 驅動橋結構型式及選擇 .91.3 主減速器設計 .101.3.1 主減速器結構方案分析 .101.3.2 單級主減速器傳動形式分析 .111.3.3 雙曲面齒輪傳動與螺旋錐齒輪傳動比較選擇 .121.4 主減速器主、從動錐齒輪的支承方案 .121.4.1 主動錐齒輪的支承方案 .131.4.2 從動錐齒輪的支承選擇 .131.5 差速器設計 .131.6 驅動車輪的傳動裝置 .141.6.1 半浮式半軸 .141.6.2 3/4 浮式 141.6.3 全浮式半軸 .151.7 驅動橋殼設計 .151.7.1 驅動橋殼應滿足如下設計要求 .151.7.2 驅動橋殼結構方案分析 .151原文：Engine Lubricating SystemThere are a great many moving metal parts in the engine . These parts must be protected by lubricating oil so that there will be protected by lubricating oil so that there will be no actual metal-to-metal contact . The moving parts , in effect , float on films of oil . Two types of lubricating systems have been used on four-cycle automotive engines , splash and combination splash and pressure feed .In the splash lubricating system , oil is splashed up from the oil pan or oil trays in the lower part of the crankcase .The oil is thrown upward so droplets or fine mist and provides adequate lubrication to valve mechanisms , piston pins , cylinder walls , and piston rings . In the splash lubricating system , oil is splashed up from the oil pan or oil trays in the lower part of the crankcase . The oil is thrown upward as droplets or fine mist and provides adequate lubrication to valve mechanisms , piston pins , cylinder walls , and piston rings .In the combination splash and pressure feed lubricating system , an oil pump takes oil from the oil from the oil pan and forces it through holes drilled in the engine block and crankshaft .This oil thereby reaches the various bearings that support rotating shafts and the different moving parts in the engine . It covers the surfaces of the moving parts to prevent metal-to-metal contact and undue wear of the parts . In this system , cylinder walls are lubricated by splashing oil thrown off from the connecting –rod bearing . The lubricating oil circulating through the engine to all moving parts requiring lubrication performs other jobs .(1) Lubricate moving parts to minimize wear .(2) Lubricate moving parts to minimize power loss from friction(3) Remove heat from engine parts by acting as a cooling agent .(4) Absorb shocks between bearings and other engine parts , thus reducing engine noise and extending engine life .(5) Form a good seal between piston rings and cylinder walls . (6) Act as a cleaning agent , washing the working surfaces free of chemical deposits , dust and dirt to protect them from corrosion . A satisfactory engine lubricating oil must have certain characteristics , or properties . It must have proper viscosity (body and fluidity ) and must resist oxidation , carbon formation , corrosion , rust , extreme pressures , and foaming . Also , it must act as a good cleaning agent , must pour at low temperatures , and must have good viscosity at extremes of high and low temperature .2Any mineral oil , by itself , does not have all these properties . Lubricating-oil manufacturers therefore put a number of additives into the oil during the manufacturing process .A oil for severe service may have many additives , as follows :(1) usually a viscosity-index improver ;(2) pour-point depressants;(3) oxidation inhibitors ;(4) corrosion inhibitors ;(5) rust inhibitors ;(6) foam inhibitors ;(7) detergent-dispersants ;(8)extreme-pressure agents. Valves and Valves Train Valves and Valve Train There are two openings , or ports , in the enclosed end of the cylinder . One of the ports permits the mixture of air and gasoline vapor to enter the cylinder . The other port permits the burned gases , after combustion , to exhaust , or escape , from the cylinder . The two pores have valves assembled into them . These valves close off one or the other port , or both ports , during the various stages of engine operation . That is to say , each cylinder has two valves , an intake valve and exhaust valve . The cam lobes on the camshaft are so related to the crankshaft crankpins through the gears or sprockets and chain as to cause the valves to open and close with the correct relationship to the piston strokes .The valves are nothing more than accurately machined metal plugs (on long stems ) that close the openings when they are seated ( have moved up into the openings ) . When the valve closes , it moves up so that the outer edge rests on the seat . In this position , the valve port is closed so that air or gas cannot escape from the cylinder .A spring on the valve stem tends to hold the valve on its seat ( closed ) . The lower end of the spring rests against the cylinder head . The upper end rests against a flat washer , or spring retainer which is attached to the valve stem by a retainer lock ( also called a keeper ) . The spring is under compression , which means that it tries to expand and therefore spring-loads the valve in the closed position .A valve-opening mechanism opens the valve , or lifts it off its seat , at certain times . On most engines , this mechanism , called the valve train , includes a cam on the camshaft , a valve lifter , a push rod ,and a rocker arm . As the camshaft turns , the cam lobe comes around under the value lifter . This raises the lifter , which in turn pushes upward on the push rod . The push rod , as it is lifted , causes the end of the rocker arm to move up . The rocker arm pivots around its supporting shaft so that the valve end of the rocker arm is forced downward . This downward movement forces the valve to move downward off its seat so that it opens . After the cam lobe moves out from under the valve lifter , the valve spring forces the valve up onto its seat again .In the other kind of valve mechanism for an engine , the valves are located in the cylinder block instead of the head . With this arrangement , the camshaft is directly below the valve lifter , and no push rods or rocker arms are necessary . Although the valve-in-block 3arrangement is a simple design . Most automotive engines are the valve-in-head type . The valve-in-head engine has certain advantages . Cam and Camshaft A cam is a device that can change rotary motion into linear , or straight-line , motion . The cam has a high spot , or lobe ; a follower riding on the cam will move away from or toward the camshaft as the cam rotates . In the engine , cams on the camshaft cause the intake and exhaust valves to open . There is s cam on the camshaft for each valve , or two cams per cylinder . The camshaft is driven by gears , or by a chain , from the crankshaft . It turns at one-half crankshaft speed . In the four –cycle engine , every two revolutions of the crankshaft produce one revolution of the camshaft and one opening and closing . The cam lobes are so positioned on the camshaft as to cause the valves to open and close in the cylinders at the proper time with respect to the actions taking place in the cylinders .In addition , the camshaft has an eccentric to operate the fuel pump and a gear to drive the ignition distributor and oil pump .Piston Connecting RodPistonThe piston is essentially a cylindrical plug that moves up and down in the engine cylinder . it is equipped with piston rings to provide a good seal between the cylinder wall and piston . The piston absorbs heat from the gas , and this heat must be carried away if the metal temperature is to be held within safe limits . The constant reversal of the piston travel sets up inertia forces , which increase both with the weight of the piston and with its speed . For this reason , designers try to keep piston weight low , particularly in high-speed engines . As lower hood lines and over square engines became popular , the semi-slipper and full-slipper pistons came into use . On these pistons the number piston rings was reduced to three , two compression and one oil-control . One reason for the slipper piston is that , on the short-stroke , over square engine , the piston skirt had to be cut away to make room for the counterweights on the crankshaft . Also , the slipper piston , being shorter and having part of its skirt cut away , is lighter . This reduces the inertia load on the engine bearings and , in addition , makes for a more responsive engine . The lighter the piston , the less the bearing load and the longer the bearings will last . Another way to lighten the piston is to make it lf light metal . The ideal piston material would be light and strong , conduct heat well , expand only slight when heated , resist wear ,and be low in cost .Thus , most automotive-engine pistons today are made of aluminum , which is less than half as heavy as iron . Iron pistons were common in the earlier engines . Aluminum expands more rapidly than iron with increasing temperature , however , and since the cylinder block is lf iron , special provisions must be made to maintain proper piston clearance at operating temperatures. To take care of it , the crown is machined on slight taper , the diameter being greatest where the crown meets the skirt and becoming less toward the top . Piston RingsA good seal must be maintained between the piston and cylinder wall to prevent blow-by . “ blow-by ” is the name that describes the escape of burned gases from the combustion chamber , past the piston , and into the crankcase . In other words , these gases “blow by ” the piston .It is not practical to fit the piston to the cylinder closely to prevent blow-by . Thus , 4piston rings must be used to provide the necessary seal . The rings are installed in grooves in the piston . Actually , there are two types of rings , compression rings and oil-control rings , The compression rings seal in the air-fuel mixture as it is compressed and also the combustion pressures as the mixture burns. The oil-control rings scrape off excessive oil from the cylinder wall and return it to the oil pan. The rings have joints (they are split ) so that they can be expanded and slipped over the piston head and into the recessed grooves cut in the piston . Rings for automotive engines usually have butt joints , but in some heavy –duty engines , the joints may be angled ,lapped , or of the sealed type .The rings are somewhat larger in diameter than they will be when en the cylinder . Then ,when they are installed , they are compressed so that the joints are nearly closed . Compressing the rings gives them an initial tension ; they press tightly against the cylinder wall .Connecting Rod The connecting rod is attached at one end to a crankpin on the crankshaft and at the other end to a piston , through a piston pin or wrist pin . The connecting rod must be very strong and rigid and also as light as possible . The connecting rod carries the power thrusts from the pioton to the crankpin . At the shame time , the rod is in eccentric motion . To minimize vibration and bearing loads , the rod must be light in weight . To maintain good engine balance , connecting rods and caps are individually matched to each other and usually carry identifying numbers so they will not be mixed if the engine is disassembled for service . They must mot be mixed during any service job , since this could result in poor bearing fit and bearing failure . Crankshaft FlywheelCrankshaft The crankshaft is a one-piece casting or forging of heat-treated alloy steel of considerable mechanical strength . The crankshaft must be strong enough to take the down ward thrusts of the pistons during the power strokes without excessive distortion . In addition , the crankshaft must be carefully balanced to eliminate undue vibration resulting from the weight of the offset cranks . To provide balance , crankshafts have counterweights opposite the cranks . Crankshafts have drilled oil passages through which oil can flow from the main to the connecting-rod bearings .The front end of the crankshaft carries three devices , the gear or sprocket that drives the camshaft , the vibration damper , and the fan belt pulley . The camshaft , the vibration damper , and the fan belt pulley . The pulley drives the engine fan , water pump ,and generator with a V belt .Flywheel The flow of power from the engine cylinders is not smooth .Although the power impulses cylinders is not smooth . Although the power impulses overlap ( on six-and eight-cylinder engines ) , there are times when more power is being delivered than at other times . This tends to make the crankshaft speed up and then slow down . However , the flywheel combats the tendency . The flywheel is a comparatively heavy wheel bolted to the tear end of the crankshaft . The inertia of the flywheel tends to keep it turning at constant speed . Thus , 5the flywheel absorbs energy as the crankshaft tries to slow down . In effect , the flywheel absorbs power from the engine during the power stroke( or speedup time ) and then gives it back to the engine during the other three strokes ( or slowdown time ) of the cycle . 6譯文發(fā)動機潤滑系統(tǒng)發(fā)動機中有大量的運動的金屬零件。要保護這些零件就必須進行潤滑，這樣可以避免金屬零件之間的直接接觸。實際上，在運動零件的表面總是覆蓋著一層油膜。四行程發(fā)動機使用兩種潤滑系統(tǒng)：飛濺式潤滑和飛濺壓力結合送油式潤滑。在飛濺潤滑系統(tǒng)中，油從機體下部的油盤或油底殼中飛濺上來。飛濺上來的油形成油滴或油霧，使氣門機構、活塞銷、氣缸壁和活塞環(huán)得到充分的潤滑。在飛濺壓力結合送油潤滑系統(tǒng)中，油泵從油盤中把油抽上來并壓入發(fā)動機機體上和曲軸上的油道，被輸送到發(fā)動機的曲軸和各種運動的零件的每個軸承上。潤滑油在運動零件表面形成油膜，以防止金屬零件表面直接接觸以及零件的過度磨損。在這一系統(tǒng)中，氣缸壁是由連桿軸承運動飛濺起來的油進行潤滑的。潤滑油在發(fā)動機的所有活動部件之間循環(huán)流動，其作用為：1. 潤滑運動零件，減少磨損。2. 潤滑運動零件，減少因磨損因素起的功率損耗。3. 其冷卻劑作用，帶走發(fā)動機零件產生的熱量。4. 吸收軸承和其他發(fā)動機零件之間產生的沖擊力，減少發(fā)動機的噪音，并延長其壽命。5. 在活塞環(huán)和氣缸壁之間形成良好的密封。6. 起清潔劑作用，沖洗運動零件表面的化學雜質、灰塵和污物，以避免部件受到腐蝕。理想的發(fā)動機潤滑油必須具有某些特性：必須具有一定的粘性（粘稠度和流動性），并且必須具有抗氧化、防止碳膜生成、防腐、防銹、抗極壓和防泡沫等作用，潤滑油必須具有良好清潔作用和良好的低溫流動性，以及在高溫和低溫時都具有良好的粘性。任何礦物油自身都不具備所有這些特性。因此，潤滑油廠家在制造潤滑油的過程中，加入了許多添加劑。高級潤滑油中可能加入以下這些添加劑：（1）常常加入黏度指數添加劑；(2)抗凝劑；（3）抗氧劑；（4）防腐劑；（5）防銹劑；（6）抗泡劑；（7）凈化分散劑；（8）極壓擠。氣門與氣門傳動組氣門和氣門機構在汽缸封閉的一端，有兩個開口，或稱為孔。一個開口使可燃混合氣可以及時進入氣缸。另一個開口是讓燃燒后的氣體從氣缸內排出。這兩個開口都裝有氣門。這些氣門在發(fā)動機工作順序的不同階段，關閉一個開口，（或另一個開口），或者同時關閉兩個開口。也就是說，每個氣缸有兩個氣門，即進氣門和排氣門。凸輪軸上的凸輪凸角通過齒輪或鏈輪和鏈條與曲軸軸頸相連，這樣，可以使氣門按照活塞行程的正確順序開啟和關閉。氣門不過是裝在閥桿上加工精細的金屬塞而已。當氣門就位時（向上移動閥口）時，即可將氣門關閉。氣門關閉時，氣門向上移動，這樣氣門的邊緣就正好落在氣門座上。在這一位置上，氣門口關閉，混合氣就不會從汽缸中逸出。7氣門桿上的彈簧使氣門保持在氣門座上（關閉狀態(tài)）。彈簧的下端抵在氣缸蓋上。上端抵在彈簧座上，在彈簧座的下面有栓銷（或叫做定位銷）加以定位。彈簧處于“壓縮”狀態(tài)時，意味著彈簧試圖伸展，氣門受彈簧作用而處于關閉狀態(tài)。使氣門開啟的機械裝置在恰當的時刻開啟氣門或者將氣門從氣門座上提起。在大多數發(fā)動機中，這套裝置的中包括凸輪軸上的一個凸輪，一個氣門挺桿，一個氣門推桿和一個搖臂。當凸輪軸轉動時，凸輪凸角轉到氣門挺桿下面，使挺桿上舉，挺桿推動推桿。當推桿升起時，搖臂的端部向上移動。搖臂圍繞支撐軸旋轉，氣門與搖臂相對應的一端壓下。向下的運動使氣門向下移動離開氣門座，氣門被打開。當凸輪凸角離開氣門挺桿，氣門彈簧使氣門重新回到氣門座上。另一種氣門機構的氣門是裝在汽缸體上，而不是汽缸蓋上。在這種裝置中，凸輪軸直接裝在氣門挺桿下，并且不必有推桿或搖臂。雖然側置氣門發(fā)動機結構設計簡單，大多數汽車發(fā)動機卻都是頂置氣門，因為頂置式氣門發(fā)動機的確有優(yōu)點。凸輪和凸輪軸凸輪是能夠使旋轉運動變?yōu)榫€性或直線運動的裝置。凸輪有一個頂點，或叫做凸輪凸角。當凸輪轉動時，凸輪上的從動件也隨著凸輪軸來回移動。在發(fā)動機中，凸輪軸上的凸輪控制進氣門和排氣門的開啟和關閉。每個氣門有一凸輪，每一個氣缸就有兩個凸輪。凸輪軸由曲軸通過正時齒輪或鏈條來驅動。凸輪軸的轉速為曲軸轉速的一半。在四行程發(fā)動機中，曲軸上凸輪凸角的位置使氣門在恰當的時候開關，以便與氣缸的工作順序相一致。此外，凸輪軸還帶動一個驅動燃料泵的偏心輪和一個帶動分電器和油泵的齒輪。活塞 連桿活塞實質上活塞是一個在氣缸中上下移動的圓筒狀的塞子，面裝有活塞環(huán),從而使活塞和氣缸之間具有良好的密封性?；钊麖臍怏w中吸熱，假如要使金屬的溫度保持在安全限度以內，就必須散熱?；钊牟粩嗤鶑瓦\動產生了慣性力，慣性力隨活塞的重量及其速度的增加而增大。為此，設計者設法使活塞造的輕些，特別是高速度發(fā)動機。由于低發(fā)動機罩和短行程發(fā)動機的進一步普及，半圍延裙活塞和滑裙式活塞開始使用。在這些活塞中，活塞環(huán)的數量減少到三個，即兩個氣環(huán)，一個油環(huán)。使用滑裙活塞的原因是：短行程發(fā)動機需除去部分活塞裙部，從而為曲軸的平衡重讓出空間?；瑒踊钊L度較短，由于裙部被部分切除后而重量較輕。這就減少了發(fā)動機軸承上的慣性負荷，使動機反應更加靈敏?；钊捷p，軸承的負荷越小,軸承的工作壽命就越長.還有一種可使活塞質量減小的方法,就是用輕金屬制造活塞.理想的活塞材料應該重量輕,強度高,導熱好,熱膨脹小,耐磨，價格低廉。因此今天大多數的汽車發(fā)動機活塞都是鋁制成的，鋁的重量還不到鑄鐵的一半。鑄鐵活塞在早期的發(fā)動機中廣泛使用。隨著溫度的增加，鋁比鑄鐵膨脹量更大。然而，由于氣缸體是鑄鐵制的，必須采用特殊的措施，以維持工作溫度下正常的活塞間隙。考慮到這一點，活塞頂部要加工成略成錐狀體，即活塞頂部與活塞裙部交接處直徑最大，愈向頂部，直徑愈小。活塞環(huán)在活塞與氣缸壁之間必須保持良好的密封以防止漏氣?！奥狻边@一名秤是指燃燒氣體從燃燒室溢出，經過活塞進入曲軸箱。換句話說，這些氣體是通過活塞溢出的。實際上，活塞與氣缸間再嚴密也免不了漏氣。所以活塞環(huán)就用來提供必要的密封?；钊h(huán)裝在活塞的凹槽中。事實上有兩種活塞環(huán)，氣環(huán)和油環(huán)。當可燃混合氣壓縮時，8氣環(huán)密封可燃混合氣；當可燃混合氣燃燒時氣環(huán)可阻止所產生的壓力不外溢。油環(huán)的作用是刮去氣缸壁上多余的機油，使之流回油底殼?；钊h(huán)有接口（也就是有一縫隙）。這樣可以使端部擴張并滑入活塞上的凹槽中。汽車發(fā)動機上的活塞環(huán)通常是有接口。但在一些重型發(fā)動機上，活塞環(huán)的接口可以使斜角接口，搭接式或是密封式的?；钊h(huán)的直徑要略大于裝入氣缸時直徑。這樣，在活塞裝入氣缸中時，活塞環(huán)就會被壓縮，接頭幾乎閉合了。受壓使之具有預張力，活塞環(huán)就緊緊的壓在氣缸壁上。連桿連桿的一端與曲軸的連桿軸頸相連，另一端通過活塞銷與活塞相連。連桿必須具有足夠的強度和剛度，并且要盡可能輕。連桿的作用是將活塞承受的壓力傳給連桿軸頸。同時，連桿做偏心運動。為了把振動和軸承負荷減小到最低限度，連桿的重量必須盡可能的輕。為了保持發(fā)動機的良好平衡，連桿和連桿蓋都要精心配套。發(fā)動機連桿的質量都必須相等，否則，就會產生明顯的振動。在進行裝配時，連桿和連桿蓋都必須一一相互匹配。為了防止拆裝發(fā)動機是發(fā)生匹配錯誤，通常在部件上刻上標號。在維修過程中，千萬不能弄混，因為這會造成軸承不配套及軸承的損壞。曲軸 飛輪曲軸曲軸是由合金鋼鑄造或鍛造，經過熱處理，具有一定的機械強度的整體結構。曲軸必須就有足夠的強度，以承受活塞在做功行程期間向下運動產生的沖力，而不會產生過度的扭曲。另外，曲軸必須仔細地給予平衡，以避免曲柄重力偏移而引起過度振動。為了保持平衡，曲軸必須具有與曲軸相對應的平衡重。曲軸上鉆有油道，潤滑油可以從主軸承流到連桿軸承上。在曲軸的前端有三個裝置：驅動凸輪軸的齒輪或鏈輪，減震器和風扇皮帶輪。皮帶輪通過 V 型皮帶驅動發(fā)動機風扇，水泵和發(fā)電機。飛輪發(fā)動機氣缸所產生的動力是不均勻的。盡管在六缸或八缸發(fā)動機中，動力沖擊重疊發(fā)生，但是有時產生的動力會大些。這會使曲軸的運轉速度忽快忽慢。然而飛輪可以克服這種傾向。飛輪是一個很重的輪子，用螺栓固定在曲軸的后端。飛輪的慣性使飛輪保持恒速運動。這樣，飛輪在曲軸加速時把能量儲存起來，當曲軸速度減慢時再釋放出來。事實上，飛輪在做功行程（或加速過程）中貯存動能，而在其它三個行程（或減慢過程）中，把動能釋放出來。9第一章 方案論證1.1 概 述驅動橋處于動力傳動系的末端，不僅是汽車的動力傳遞機構，也是行走機構。其基本功能是增大由傳動軸或變速器傳來餓轉矩，并將動力合理地分配給左、右驅動功能。驅動橋是汽車傳動系中的主要總成之一。驅動橋的設計是否合理直接關系到汽車使用性能的好壞。因此，驅動橋設計應當滿足以下基本要求：1）所選擇的主減速比應能滿足汽車在給定使用條件下具有最佳的動力性和燃油經濟性；2）差速器在保證左、右驅動車輪能以汽車運動學所要求的差速滾動外并能將轉矩平穩(wěn)而連續(xù)不斷（無脈動）地傳遞給左右驅動車輪；3）當左右驅動車輪與地面的；4） 在各種轉速和載荷下，具有高的傳動效率；5）在保證足夠的強度、剛度條件下，應力求質量小，尤其是簧下質量應盡量小，以改善汽車平順性；6）與懸架導向機構運動協(xié)調；7）結構簡單，加工工藝性好，制造容易，折裝、調整方便。驅動橋一般由主減速器、半軸和驅動橋殼組成。各部分功用如下：主減速器：將低由傳動軸傳來的轉速并增大扭矩。差速器：在兩輸出軸間分配轉矩并保證兩輸出軸可能以不同的轉速旋轉。半軸：接受并傳遞轉矩到兩邊驅動車輪。驅動橋殼：支承汽車整體質量，并承受由車輪傳來的由路面不平引起的反力和反力矩，并經懸架傳遞給支架或車身。1.2 驅動橋結構型式及選擇驅動橋的結構形式與驅動車輪的懸架形式密切相關。當車輪采用非獨立懸架時，驅動橋應為非斷開式；當車輪采用獨立懸架時，驅動橋應為斷開式?，F把它們各自的結構特點分析（如：表 1）：表 1 驅動橋結構型式及選擇形式 非斷開驅動橋 斷開驅動橋10特點結構特點橋殼是一根支承在左、右驅動輪上的剛性空心梁，而主減速器、差速器和半軸等傳動部件都裝在其內；整個驅動橋通過懸架與支架或車身連接橋殼分段，彼此之間用鉸鏈連接，可作相對運動；主減速器、差速器等固定在支架或車身上，兩側驅動輪通過獨立懸架與支架或車身連接，兩輪可彼此獨立地相對于支架或車身上下跳動優(yōu)點結構簡單，制造工藝性好，成本低，工作可靠，維修和調整容易減低簧下質量從而改善汽車通過性，提高行使平順性，平均車速提高。降低車輪和車橋上的動載荷，提高了零部件的使用壽命。與地面接觸良好，抗側滑能力提高，汽車的持縱穩(wěn)定性更好缺點 簧下質量大，對降低動載荷不利，平順性差，Hmin小，通過性不好結構復雜，成本較高應用 各種貨車、客車及多數越野車和部分轎車越野車、轎車轎車行使的路面條件較好，故采用非斷開式驅動橋1.3 主減速器設計1.3.1 主減速器結構方案分析汽車的主減速器有單級主減速器和雙級主減速器，減速型式的選擇與汽車的類型及使用條件有關，有時也與制造廠已有的產品系列及制造條件有關，但它主要取決于11由動力性、經濟性等整車性能所要求的主減速比 i0的大小及驅動橋下的離地間隙、驅動橋的數目及布置型式等。本車型采用單級主減速器，由于單級主減速器具有結構簡單、質量小、尺寸緊湊及制造成本低等優(yōu)點，因而廣泛地用在主減速比 i0≤7.6 的各種中小型汽車上。例如：轎車、輕型載貨汽車都是采用單級主減速器，大多數中型載貨汽車也采用這種型式。而雙級主減速器由兩級齒輪副組成，結構復雜、質量加大，制造成本也顯著增加，因此僅用于主減速比較大（7.6＜i 0≤12）且單級減速不能滿足既定的主減速比和離地間隙要求的重型汽車上。以往在某些中型載貨汽車上雖有采用，但在新設計的現代中型載貨汽車上已很少見了。這是由于隨著發(fā)動機功率的提高車輛整備質量的減小以及路面狀況的改善，中等以下噸位的載貨汽車往往具有更高車速的方向發(fā)展，因而需采用較小主減速比的緣故。1.3.2 單級主減速器傳動形式分析單級主減速器傳動形式主要有四種：螺旋錐齒輪傳動、雙曲面齒輪傳動、圓柱齒輪傳動和蝸輪蝸桿傳動。它們的傳動形式如圖：（a） (b) (c) (d)螺旋錐齒輪傳動 雙曲面齒輪傳動 圓柱齒輪傳動 蝸輪蝸桿傳動圖 1 單級主減速器傳動形式（一） 螺旋錐齒輪傳動螺旋錐齒輪傳動的主、從動齒輪軸線垂直相交于一點，齒輪并不同時在全長上齒合，而是逐漸從一端連續(xù)平穩(wěn)地轉移向另一端，另外，由于輪齒端面重疊的影響，至少有兩對以上的輪齒同時齒合，所以它工作平穩(wěn)，能承受較大的負荷，制造也簡單。但在工作中噪聲大，對齒合精度很敏感，齒輪副錐頂稍有不吻合便會使工作條件急劇變壞，并伴隨磨損增大而噪聲增大。為保證齒輪副的正確齒合，必須將支承軸承預緊，提高了支承剛度，增大殼體剛度。（二） 雙曲面齒輪傳動雙曲面齒輪傳動的主、從動齒輪的軸線相互垂直而不相交，主動齒輪軸線相對從12動齒輪軸線在空間偏移一距離 E（偏移距） ，由于偏移距的存在，使主動齒輪螺旋角β 1大于從動齒輪螺旋角 β 2，從而使雙曲面齒輪傳動比大于相同尺寸的螺旋錐齒輪傳動比。（三） 圓柱齒輪傳動圓柱齒輪傳動一般采用斜齒輪，廣泛應用于發(fā)動機橫置且前置前驅動的轎車驅動橋和雙級主減速器置通式驅動橋。（四） 蝸桿蝸輪傳動蝸桿蝸輪傳動比較大（i 0﹥7）在任何轉速使用下均能工作非常平穩(wěn)且無噪聲，便于汽車的總布置及貫通式多橋驅動的布置，能傳遞大的載荷，使用壽命長，結構簡單，折裝方便，調整容易。但制造成本高，傳動效率低，應用于重型多橋驅動汽車和具有高轉速發(fā)動機的大客車上。1.3.3 雙曲面齒輪傳動與螺旋錐齒輪傳動比較選擇表 2 從動輪的選擇類型 雙曲面齒輪 螺旋錐齒輪優(yōu)點兩者尺寸相同時，此種齒輪傳動比 i0大，當 i0一定且從動齒輪尺寸相同時，此類齒輪直徑大，輪齒強度大，剛度大。當 i0一定，主動齒輪尺寸相同，此類齒輪 Hmin 較大。此類齒輪有側向滑動和縱向滑動，縱向滑動可使其運轉平穩(wěn)。β 1β 2，重合度大，可提高傳動平穩(wěn)性和彎曲強度。其主動齒輪較大，加工時所需刀盤刀頂距較大，因而切削刃壽命較長。由于螺旋角較大，摩擦損失較小，傳動效率高達 99%，抗膠合能力強，軸承負荷小，潤滑成本低。缺點縱向滑動增加摩擦損失，傳動效率較低約為 96%，抗膠合能力低，軸向力大，軸承負荷大，潤滑成本高。同尺寸時傳動比小，同傳動比時齒輪強度和剛度較小。Hmin 小。選取 螺旋錐齒輪傳動131.4 主減速器主、從動錐齒輪的支承方案主減速器中心須保證主、從齒輪具有良好的齒合狀況才能使它們很好地工作，齒輪的正確齒合除與齒輪的加工質量、裝配調整及軸承、主減速器殼體的剛度有關外，還與齒輪的支承剛度密切相關。1.4.1 主動錐齒輪的支承方案現代汽車的主動錐齒輪的支承型式有懸臂式和騎馬式。懸臂式一其齒輪大端一側的軸頸支承在相距比齒寬中點的懸臂長大兩倍以上的一對軸承上；騎馬式在齒輪小端前增裝一個稱為導向軸承的圓柱滾子軸承，且大端一側的軸承靠近，也稱兩端支承式和跨置式。懸臂式支承通常用在傳動轉矩較小的轎車、輕型貨車上。在中型和重型貨車上的雙級主減速器中，由于布置空間的困難，也采用這種支承方式。采用跨置式支承時齒輪承載能力較懸臂式支承提高 10%左右，提高了支承剛度，并使軸承負荷減小，改善齒輪嚙合條件。此外，由于齒輪軸頸上的兩個圓錐滾子軸承間距很小，可以縮短主動齒輪軸的長度，使布置更緊湊，并可減少傳動軸夾角，有利于整車布置。但是，由于主、從動錐齒輪間的空間有限，致使主動錐齒輪小端處的支承座和軸承尺寸受到限制。增加了主動錐齒輪小端前支承后也給主減速器殼體的鑄造及機械加工帶來了困難。目前，跨置式支承主要用在需要傳遞較大扭矩的情況下，在中型和重型的單級主減速器中得到廣泛的應用。參考所選車型屬于轎車，因此主減速器主動錐齒輪采用懸臂式支承。1.4.2 從動錐齒輪的支承選擇影響因素：軸承的支承形式，軸承間的距離，軸承上的載荷分布。因為載貨汽車主動錐齒輪的支承采用懸臂式支承。從動錐齒輪的支承采用圓錐滾子軸承支承，兩軸承的圓錐滾子大端向內，以增加支承剛度。這樣即滿足了要求又節(jié)約了成本。1.5 差速器設計汽車在行駛過程中，左右車輪在同一時間內所滾過的路程往往是不相等的，特別是在轉彎時外車輪比內車輪滾過的路程多，如果兩車輪剛性連接，則會引起車輪在路面上滑拖或滑轉，這樣，一方面會加劇車輪磨損、功率和燃料消耗，另一方面會使轉向沉重，通過性和操作穩(wěn)定性變壞。為此，在左右車輪間裝有輪間差速器。差速器用14來在兩輸出軸間分配轉矩，并保證兩輸出軸有可能以不同角度轉動。差速器結構形式選擇：汽車差速器的結構形式很多，用得最廣泛的是對稱式圓錐行星齒輪差速器，大多數汽車都屬于公路運輸車輛，對于在公路上和市區(qū)行駛的汽車來說，如大客車，由于路面較好，各驅動車輪與路面的附著系數變化很小，因此幾乎都采用了結構簡單、工作平穩(wěn)、制造方便，用于公路汽車也很可靠的普通對稱式圓錐行星齒輪差速器，作為安裝在左右驅動輪間的所謂輪間差速器作用，對于經常行駛在泥濘、松軟土路或無路地區(qū)的越野汽車來說，為了防止因某一側驅動車輪滑轉而陷車，則可采用防滑差速器，后者又可分為強制鎖止式和自鎖式兩類。自鎖式差速器又有多種結構形式的高摩擦式和自由輪式的以及變傳動式的。選?。浩胀▽?/div>
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