汽车单级驱动桥总成设计-轿车驱动桥设计【三维UG】
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目 录原文：1译文6第一章 方案论证91.1 主减速器结构方案分析91.2 驱动桥结构型式及选择91.3 主减速器设计101.3.1 主减速器结构方案分析101.3.2 单级主减速器传动形式分析111.3.3 双曲面齿轮传动与螺旋锥齿轮传动比较选择121.4 主减速器主、从动锥齿轮的支承方案121.4.1 主动锥齿轮的支承方案131.4.2 从动锥齿轮的支承选择131.5 差速器设计131.6 驱动车轮的传动装置141.6.1 半浮式半轴141.6.2 3/4浮式141.6.3 全浮式半轴151.7 驱动桥壳设计151.7.1 驱动桥壳应满足如下设计要求151.7.2 驱动桥壳结构方案分析151广西工学院2011届毕业设计说明书原文：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 .Any 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 arrangement 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 , piston 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 , the 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 . 译文发动机润滑系统发动机中有大量的运动的金属零件。要保护这些零件就必须进行润滑，这样可以避免金属零件之间的直接接触。实际上，在运动零件的表面总是覆盖着一层油膜。四行程发动机使用两种润滑系统：飞溅式润滑和飞溅压力结合送油式润滑。在飞溅润滑系统中，油从机体下部的油盘或油底壳中飞溅上来。飞溅上来的油形成油滴或油雾，使气门机构、活塞销、气缸壁和活塞环得到充分的润滑。在飞溅压力结合送油润滑系统中，油泵从油盘中把油抽上来并压入发动机机体上和曲轴上的油道，被输送到发动机的曲轴和各种运动的零件的每个轴承上。润滑油在运动零件表面形成油膜，以防止金属零件表面直接接触以及零件的过度磨损。在这一系统中，气缸壁是由连杆轴承运动飞溅起来的油进行润滑的。润滑油在发动机的所有活动部件之间循环流动，其作用为：1. 润滑运动零件，减少磨损。2. 润滑运动零件，减少因磨损因素起的功率损耗。3. 其冷却剂作用，带走发动机零件产生的热量。4. 吸收轴承和其他发动机零件之间产生的冲击力，减少发动机的噪音，并延长其寿命。5. 在活塞环和气缸壁之间形成良好的密封。6. 起清洁剂作用，冲洗运动零件表面的化学杂质、灰尘和污物，以避免部件受到腐蚀。理想的发动机润滑油必须具有某些特性：必须具有一定的粘性（粘稠度和流动性），并且必须具有抗氧化、防止碳膜生成、防腐、防锈、抗极压和防泡沫等作用，润滑油必须具有良好清洁作用和良好的低温流动性，以及在高温和低温时都具有良好的粘性。任何矿物油自身都不具备所有这些特性。因此，润滑油厂家在制造润滑油的过程中，加入了许多添加剂。高级润滑油中可能加入以下这些添加剂：（1）常常加入黏度指数添加剂；(2)抗凝剂；（3）抗氧剂；（4）防腐剂；（5）防锈剂；（6）抗泡剂；（7）净化分散剂；（8）极压挤。气门与气门传动组气门和气门机构在汽缸封闭的一端，有两个开口，或称为孔。一个开口使可燃混合气可以及时进入气缸。另一个开口是让燃烧后的气体从气缸内排出。这两个开口都装有气门。这些气门在发动机工作顺序的不同阶段，关闭一个开口，（或另一个开口），或者同时关闭两个开口。也就是说，每个气缸有两个气门，即进气门和排气门。凸轮轴上的凸轮凸角通过齿轮或链轮和链条与曲轴轴颈相连，这样，可以使气门按照活塞行程的正确顺序开启和关闭。气门不过是装在阀杆上加工精细的金属塞而已。当气门就位时（向上移动阀口）时，即可将气门关闭。气门关闭时，气门向上移动，这样气门的边缘就正好落在气门座上。在这一位置上，气门口关闭，混合气就不会从汽缸中逸出。气门杆上的弹簧使气门保持在气门座上（关闭状态）。弹簧的下端抵在气缸盖上。上端抵在弹簧座上，在弹簧座的下面有栓销（或叫做定位销）加以定位。弹簧处于“压缩”状态时，意味着弹簧试图伸展，气门受弹簧作用而处于关闭状态。使气门开启的机械装置在恰当的时刻开启气门或者将气门从气门座上提起。在大多数发动机中，这套装置的中包括凸轮轴上的一个凸轮，一个气门挺杆，一个气门推杆和一个摇臂。当凸轮轴转动时，凸轮凸角转到气门挺杆下面，使挺杆上举，挺杆推动推杆。当推杆升起时，摇臂的端部向上移动。摇臂围绕支撑轴旋转，气门与摇臂相对应的一端压下。向下的运动使气门向下移动离开气门座，气门被打开。当凸轮凸角离开气门挺杆，气门弹簧使气门重新回到气门座上。另一种气门机构的气门是装在汽缸体上，而不是汽缸盖上。在这种装置中，凸轮轴直接装在气门挺杆下，并且不必有推杆或摇臂。虽然侧置气门发动机结构设计简单，大多数汽车发动机却都是顶置气门，因为顶置式气门发动机的确有优点。凸轮和凸轮轴凸轮是能够使旋转运动变为线性或直线运动的装置。凸轮有一个顶点，或叫做凸轮凸角。当凸轮转动时，凸轮上的从动件也随着凸轮轴来回移动。在发动机中，凸轮轴上的凸轮控制进气门和排气门的开启和关闭。每个气门有一凸轮，每一个气缸就有两个凸轮。凸轮轴由曲轴通过正时齿轮或链条来驱动。凸轮轴的转速为曲轴转速的一半。在四行程发动机中，曲轴上凸轮凸角的位置使气门在恰当的时候开关，以便与气缸的工作顺序相一致。此外，凸轮轴还带动一个驱动燃料泵的偏心轮和一个带动分电器和油泵的齿轮。活塞 连杆活塞实质上活塞是一个在气缸中上下移动的圆筒状的塞子，面装有活塞环,从而使活塞和气缸之间具有良好的密封性。活塞从气体中吸热，假如要使金属的温度保持在安全限度以内，就必须散热。活塞的不断往复运动产生了惯性力，惯性力随活塞的重量及其速度的增加而增大。为此，设计者设法使活塞造的轻些，特别是高速度发动机。由于低发动机罩和短行程发动机的进一步普及，半围延裙活塞和滑裙式活塞开始使用。在这些活塞中，活塞环的数量减少到三个，即两个气环，一个油环。使用滑裙活塞的原因是：短行程发动机需除去部分活塞裙部，从而为曲轴的平衡重让出空间。滑动活塞长度较短，由于裙部被部分切除后而重量较轻。这就减少了发动机轴承上的惯性负荷，使动机反应更加灵敏。活塞越轻，轴承的负荷越小,轴承的工作寿命就越长.还有一种可使活塞质量减小的方法,就是用轻金属制造活塞.理想的活塞材料应该重量轻,强度高,导热好,热膨胀小,耐磨，价格低廉。因此今天大多数的汽车发动机活塞都是铝制成的，铝的重量还不到铸铁的一半。铸铁活塞在早期的发动机中广泛使用。随着温度的增加，铝比铸铁膨胀量更大。然而，由于气缸体是铸铁制的，必须采用特殊的措施，以维持工作温度下正常的活塞间隙。考虑到这一点，活塞顶部要加工成略成锥状体，即活塞顶部与活塞裙部交接处直径最大，愈向顶部，直径愈小。 活塞环 在活塞与气缸壁之间必须保持良好的密封以防止漏气。“漏气”这一名秤是指燃烧气体从燃烧室溢出，经过活塞进入曲轴箱。换句话说，这些气体是通过活塞溢出的。实际上，活塞与气缸间再严密也免不了漏气。所以活塞环就用来提供必要的密封。活塞环装在活塞的凹槽中。事实上有两种活塞环，气环和油环。当可燃混合气压缩时，气环密封可燃混合气；当可燃混合气燃烧时气环可阻止所产生的压力不外溢。油环的作用是刮去气缸壁上多余的机油，使之流回油底壳。活塞环有接口（也就是有一缝隙）。这样可以使端部扩张并滑入活塞上的凹槽中。汽车发动机上的活塞环通常是有接口。但在一些重型发动机上，活塞环的接口可以使斜角接口，搭接式或是密封式的。活塞环的直径要略大于装入气缸时直径。这样，在活塞装入气缸中时，活塞环就会被压缩，接头几乎闭合了。受压使之具有预张力，活塞环就紧紧的压在气缸壁上。连杆连杆的一端与曲轴的连杆轴颈相连，另一端通过活塞销与活塞相连。连杆必须具有足够的强度和刚度，并且要尽可能轻。连杆的作用是将活塞承受的压力传给连杆轴颈。同时，连杆做偏心运动。为了把振动和轴承负荷减小到最低限度，连杆的重量必须尽可能的轻。为了保持发动机的良好平衡，连杆和连杆盖都要精心配套。发动机连杆的质量都必须相等，否则，就会产生明显的振动。在进行装配时，连杆和连杆盖都必须一一相互匹配。为了防止拆装发动机是发生匹配错误，通常在部件上刻上标号。在维修过程中，千万不能弄混，因为这会造成轴承不配套及轴承的损坏。曲轴 飞轮曲轴曲轴是由合金钢铸造或锻造，经过热处理，具有一定的机械强度的整体结构。曲轴必须就有足够的强度，以承受活塞在做功行程期间向下运动产生的冲力，而不会产生过度的扭曲。另外，曲轴必须仔细地给予平衡，以避免曲柄重力偏移而引起过度振动。为了保持平衡，曲轴必须具有与曲轴相对应的平衡重。曲轴上钻有油道，润滑油可以从主轴承流到连杆轴承上。在曲轴的前端有三个装置：驱动凸轮轴的齿轮或链轮，减震器和风扇皮带轮。皮带轮通过V型皮带驱动发动机风扇，水泵和发电机。飞轮发动机气缸所产生的动力是不均匀的。尽管在六缸或八缸发动机中，动力冲击重叠发生，但是有时产生的动力会大些。这会使曲轴的运转速度忽快忽慢。然而飞轮可以克服这种倾向。飞轮是一个很重的轮子，用螺栓固定在曲轴的后端。飞轮的惯性使飞轮保持恒速运动。这样，飞轮在曲轴加速时把能量储存起来，当曲轴速度减慢时再释放出来。事实上，飞轮在做功行程（或加速过程）中贮存动能，而在其它三个行程（或减慢过程）中，把动能释放出来。第一章 方案论证1.1 概 述驱动桥处于动力传动系的末端，不仅是汽车的动力传递机构，也是行走机构。其基本功能是增大由传动轴或变速器传来饿转矩，并将动力合理地分配给左、右驱动功能。驱动桥是汽车传动系中的主要总成之一。驱动桥的设计是否合理直接关系到汽车使用性能的好坏。因此，驱动桥设计应当满足以下基本要求：1） 所选择的主减速比应能满足汽车在给定使用条件下具有最佳的动力性和燃油经济性；2） 差速器在保证左、右驱动车轮能以汽车运动学所要求的差速滚动外并能将转矩平稳而连续不断（无脉动）地传递给左右驱动车轮；3） 当左右驱动车轮与地面的；4） 在各种转速和载荷下，具有高的传动效率；5） 在保证足够的强度、刚度条件下，应力求质量小，尤其是簧下质量应尽量小，以改善汽车平顺性；6） 与悬架导向机构运动协调；7） 结构简单，加工工艺性好，制造容易，折装、调整方便。驱动桥一般由主减速器、半轴和驱动桥壳组成。各部分功用如下：主减速器：将低由传动轴传来的转速并增大扭矩。差速器：在两输出轴间分配转矩并保证两输出轴可能以不同的转速旋转。半轴：接受并传递转矩到两边驱动车轮。驱动桥壳：支承汽车整体质量，并承受由车轮传来的由路面不平引起的反力和反力矩，并经悬架传递给支架或车身。1.2 驱动桥结构型式及选择驱动桥的结构形式与驱动车轮的悬架形式密切相关。当车轮采用非独立悬架时，驱动桥应为非断开式；当车轮采用独立悬架时，驱动桥应为断开式。现把它们各自的结构特点分析（如：表1）：表 1驱动桥结构型式及选择形式非断开驱动桥断开驱动桥特点结构特点桥壳是一根支承在左、右驱动轮上的刚性空心梁，而主减速器、差速器和半轴等传动部件都装在其内；整个驱动桥通过悬架与支架或车身连接桥壳分段，彼此之间用铰链连接，可作相对运动；主减速器、差速器等固定在支架或车身上，两侧驱动轮通过独立悬架与支架或车身连接，两轮可彼此独立地相对于支架或车身上下跳动优点结构简单，制造工艺性好，成本低，工作可靠，维修和调整容易减低簧下质量从而改善汽车通过性，提高行使平顺性，平均车速提高。降低车轮和车桥上的动载荷，提高了零部件的使用寿命。与地面接触良好，抗侧滑能力提高，汽车的持纵稳定性更好缺点簧下质量大，对降低动载荷不利，平顺性差，Hmin小，通过性不好结构复杂，成本较高应用各种货车、客车及多数越野车和部分轿车越野车、轿车轿车行使的路面条件较好，故采用非断开式驱动桥1.3 主减速器设计1.3.1 主减速器结构方案分析汽车的主减速器有单级主减速器和双级主减速器，减速型式的选择与汽车的类型及使用条件有关，有时也与制造厂已有的产品系列及制造条件有关，但它主要取决于由动力性、经济性等整车性能所要求的主减速比i0的大小及驱动桥下的离地间隙、驱动桥的数目及布置型式等。本车型采用单级主减速器，由于单级主减速器具有结构简单、质量小、尺寸紧凑及制造成本低等优点，因而广泛地用在主减速比i07.6的各种中小型汽车上。例如：轿车、轻型载货汽车都是采用单级主减速器，大多数中型载货汽车也采用这种型式。而双级主减速器由两级齿轮副组成，结构复杂、质量加大，制造成本也显著增加，因此仅用于主减速比较大（7.6i012）且单级减速不能满足既定的主减速比和离地间隙要求的重型汽车上。以往在某些中型载货汽车上虽有采用，但在新设计的现代中型载货汽车上已很少见了。这是由于随着发动机功率的提高车辆整备质量的减小以及路面状况的改善，中等以下吨位的载货汽车往往具有更高车速的方向发展，因而需采用较小主减速比的缘故。1.3.2 单级主减速器传动形式分析单级主减速器传动形式主要有四种：螺旋锥齿轮传动、双曲面齿轮传动、圆柱齿轮传动和蜗轮蜗杆传动。它们的传动形式如图：（a） (b) (c) (d)螺旋锥齿轮传动 双曲面齿轮传动 圆柱齿轮传动 蜗轮蜗杆传动图1单级主减速器传动形式（一） 螺旋锥齿轮传动螺旋锥齿轮传动的主、从动齿轮轴线垂直相交于一点，齿轮并不同时在全长上齿合，而是逐渐从一端连续平稳地转移向另一端，另外，由于轮齿端面重叠的影响，至少有两对以上的轮齿同时齿合，所以它工作平稳，能承受较大的负荷，制造也简单。但在工作中噪声大，对齿合精度很敏感，齿轮副锥顶稍有不吻合便会使工作条件急剧变坏，并伴随磨损增大而噪声增大。为保证齿轮副的正确齿合，必须将支承轴承预紧，提高了支承刚度，增大壳体刚度。（二） 双曲面齿轮传动双曲面齿轮传动的主、从动齿轮的轴线相互垂直而不相交，主动齿轮轴线相对从动齿轮轴线在空间偏移一距离E（偏移距），由于偏移距的存在，使主动齿轮螺旋角1大于从动齿轮螺旋角2，从而使双曲面齿轮传动比大于相同尺寸的螺旋锥齿轮传动比。（三） 圆柱齿轮传动圆柱齿轮传动一般采用斜齿轮，广泛应用于发动机横置且前置前驱动的轿车驱动桥和双级主减速器置通式驱动桥。（四） 蜗杆蜗轮传动蜗杆蜗轮传动比较大（i07）在任何转速使用下均能工作非常平稳且无噪声，便于汽车的总布置及贯通式多桥驱动的布置，能传递大的载荷，使用寿命长，结构简单，折装方便，调整容易。但制造成本高，传动效率低，应用于重型多桥驱动汽车和具有高转速发动机的大客车上。1.3.3 双曲面齿轮传动与螺旋锥齿轮传动比较选择表2从动轮的选择类型双曲面齿轮螺旋锥齿轮优点两者尺寸相同时，此种齿轮传动比i0大，当i0一定且从动齿轮尺寸相同时，此类齿轮直径大，轮齿强度大，刚度大。当i0一定，主动齿轮尺寸相同，此类齿轮Hmin较大。此类齿轮有侧向滑动和纵向滑动，纵向滑动可使其运转平稳。12，重合度大，可提高传动平稳性和弯曲强度。其主动齿轮较大，加工时所需刀盘刀顶距较大，因而切削刃寿命较长。由于螺旋角较大，摩擦损失较小，传动效率高达99%，抗胶合能力强，轴承负荷小，润滑成本低。缺点纵向滑动增加摩擦损失，传动效率较低约为96%，抗胶合能力低，轴向力大，轴承负荷大，润滑成本高。同尺寸时传动比小，同传动比时齿轮强度和刚度较小。Hmin小。选取螺旋锥齿轮传动1.4 主减速器主、从动锥齿轮的支承方案 主减速器中心须保证主、从齿轮具有良好的齿合状况才能使它们很好地工作，齿轮的正确齿合除与齿轮的加工质量、装配调整及轴承、主减速器壳体的刚度有关外，还与齿轮的支承刚度密切相关。1.4.1主动锥齿轮的支承方案现代汽车的主动锥齿轮的支承型式有悬臂式和骑马式。悬臂式一其齿轮大端一侧的轴颈支承在相距比齿宽中点的悬臂长大两倍以上的一对轴承上；骑马式在齿轮小端前增装一个称为导向轴承的圆柱滚子轴承，且大端一侧的轴承靠近，也称两端支承式和跨置式。悬臂式支承通常用在传动转矩较小的轿车、轻型货车上。在中型和重型货车上的双级主减速器中，由于布置空间的困难，也采用这种支承方式。采用跨置式支承时齿轮承载能力较悬臂式支承提高10%左右，提高了支承刚度，并使轴承负荷减小，改善齿轮啮合条件。此外，由于齿轮轴颈上的两个圆锥滚子轴承间距很小，可以缩短主动齿轮轴的长度，使布置更紧凑，并可减少传动轴夹角，有利于整车布置。但是，由于主、从动锥齿轮间的空间有限，致使主动锥齿轮小端处的支承座和轴承尺寸受到限制。增加了主动锥齿轮小端前支承后也给主减速器壳体的铸造及机械加工带来了困难。目前，跨置式支承主要用在需要传递较大扭矩的情况下，在中型和重型的单级主减速器中得到广泛的应用。参考所选车型属于轿车，因此主减速器主动锥齿轮采用悬臂式支承。1.4.2从动锥齿轮的支承选择影响因素：轴承的支承形式，轴承间的距离，轴承上的载荷分布。因为载货汽车
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