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1、DRIVE AXLE ASSEMBLIESAfter studying this chapter, you will be able to: Explain the construction of different types of drive axle assemblies.List the parts of various drive axles. Compare the differences between a rear wheel and front wheel drive axle assembly.Describe the operating principles of dri
2、ve axle assemblies.Drive axle assemblies have several important functions. They must hold the wheels on, keep them upright, allow them to be turned (in front, on four-wheel drive and front-wheel drive vehicles) and propel the wheels forward or backward. They must drive the wheels in such a manner th
3、at one can turn faster than the other, yet both must receive torque. Drive axle assemblies must absorb the driving force of the wheels, and transmit it to the frame through springs, control rods, etc. The axle assembly provides an anchorage for springs, supports the weight of the vehicle and forms t
4、he foundation upon which the wheel brakes are mounted. Obviously, the axle assemblies must be well constructed, using quality materials.HOUSING The axle housing is usually made of stamped steel parts welded together. Or, the center section of the housing may be made of cast steel. Two basic types ha
5、ve been used: the BANJO type housing (in wide use) and the SPLIT housing (little used) consisting of two or more pieces. AXLES Two steel axles are placed inside the housing. Their inner ends almost touch; and, in some cases, they do touch. The outer ends protrude out of the housing and form a base u
6、pon which the wheels, hubs, etc. are attached. The inner ends are splined and are supported by the differential assembly. The outer ends are supported in roller or hall bearings. ATTACHING WHEEL HUBS Two methods are employed to securc the wheelhubs to the axle. One emthod employs a taper on the axle
7、 end; tile other forms the axle end into a flange upon which the wheel is bolted. TYPES OF AXLES Live axles (axles that turn with the wheels) are of three basic types: full-floating, three-quarter-floating and semifloating. Most cars utilize the semi floating axle. Most trucks have full-floating axl
8、es. If tile axle breaks, tile wheel will not come off. Tile three types .DRIVING THE AXLES The real wheels of a vehicle must turn at different speeds when rounding the slightest corner (outside wheel must roll farther). Therefore, it is necessary to employ a unit called a DIFFEREN FIAL to drive the
9、axles so both axles receive power, yet they are free to turn at different speeds.THE DIFFERENTIAL A splined axle side gear is placed on tile innersplined end of each axle. 1he axle side gear is supported by the differential case. The side gear is free to turn ill the case. The differential case may
10、be turned. It will revolve about the axle side gears. The differential pinion shaft will turn with the case, bur tile axle side gears will not be driven. By bolting a large ring gear to the differential case. and connecting it to a ring gear pinion gear and shaft, it will be possible to turn the cas
11、e. The propeller shaft will be attached lo the ring gear pinion shaft. When the propeller shaft turns the ring gear pinion, the pinion will turn the ring gear. The ring gear, in turn will revolve the differential case and pinion shaft. Tile axle side gears will still NOT TURN. By adding two differen
12、tial pinion gears (the differential pinion shaft will pass through these gears) that mesh with the side gears, the revolving case will turn the axle side gears with it. DIFFERENTIAL ACTION The propeller shaft turns tile ring gear pinion shaft. The ring gear pinion turns the ring gear which, in turn,
13、 revolves the differential case. When the case turns, the differential pinion shaft turns with it. As the differential pinions are mounted on this shaft, they are forced to move with the case. Being meshed with the axle side gears, the pinions will pull the axle side gears along with them. When the
14、car is moving in a straight line, the ring gear is spinning the case. The differential pinions and axle side gears arc moving around with the case, with no movement between the teeth of the pinions and axle side gears. The entire movement is like a solid unit.When rounding a turn, the case continues
15、 whirlingand pulling the pinions around on the shaft. As the outer wheel must turn faster, the outer axle side gear is now moving faster than the inner axle side gear. The whirIing pinions not only pull on both axle sidegears, but now begin to rotate on their shaft.Auto Mechanics Fundamentalswhile w
16、alking in the axle side gears. This allows them to pull on both axle side gears, while at the same time, compensating for difference in speed by rotating around their shaft. You can see detail A, the car is moving in a straight line. The pinion is pulling both gears, but it is not turning. In B, the
17、 right side axle gear is moving faster than the left axle gear. The pinion gear is still moving at the same speed. It is still pulling on both gears, but has now started to turn on the pinion shaft. This turning action, added to the forward rotational speed of the shaft, has caused the right-hand si
18、de gear to speed up and actually begin to pass the pinion shaft. Study Figs. 16-9 and 16-10. The reversewalking effect on the left-hand side gear has caused it to slow down. The differential action adjusts itself to any axle speed variation. If one wheel begins to slip, the axle on firm ground will
19、stand still. The case continues spinning the pinions, but they will merely walk around the stopped axle gear and impart the torque to the spinning axle. A special traction differential is often used to overcome this tendency. It will be covered later in this chapter.DIFFERENTIAL CARRIER AND BEARINGS
20、A heavy and rigid section is bolted to the housing. It contains the pinion gear, shaft, and bearings. This is termed the DIFFERENTIAL CARRIER. Two large bearing holders are provided to support the spinning differential case. These are termed CARRIER BEARINGS. In some applications, the carrier is mad
21、e as a solid part of the axle housing. All the component parts of the axle housing, axles and differentialSPECIAL TRACTION DIFFERENTIAL To avoid the loss of driving force that occurs when one wheel begins to slip, special differentials are designed to automatically transfer the torque to the wheel t
22、hat is not slipping. This enables the car to continue its forward motion. Although there are several variations, all employ the principle of a friction device (clutch plates or a cone clutch) to provide some resistance to normal differential action.CHRYSLER SURE-GRIP The Chrysler Sure-Grip different
23、ial is basically a standard model, but with several important additions. The axle side gears are driven not by two differential pinions but by four. This requires two separate pinion shafts.The two shafts cross, but are free to move in-dependently of each other, The shaft outer ends are not round, b
24、ut have two flat surfaces that form a shallow V. These ramp-like surfaces engage similar ramps cut in the differential case. A series of four clutch discs are used in back of each axle side gear thrust member. Two of these discs are splined to the differential case, and two are splined to the thrust
25、 member. The thrust member is splined to the axle. When the thrust members push outward, the clutch discs are forced together, locking the axle to the case. SURE-GRIP DIFFERENTIALOPERATION-BOTH AXLES TURNING AT THE SAME SPEEDWhen the propeller shaft drives the pinion gear, the torque thrust is trans
26、mitted to the ring gear. As the ring gear drives the differential case, the pinion shafts are forced to rotate with the case. The differential pinions encounter resistance when they attempt to turn the axle side gears. This resistance is transferred to the pinion shafts that aredriving the pinions.
27、As both ends of each pinion shaft are seated in tapered ramps, and since they have some play at this point, this forces the shafts to slide up the ramp surfaces. This sliding movement moves bothshafts n an outward direction. As each shaft moves outward, it moves its pinions in the same direction. Th
28、e pinions press against the pinion thrust members, forcing them to lock up the clutches. This is the action when the car is traveling in a straight line. AXLES TURNING AT DIFFERENT SPEEDSWhen the car turns a corner, the inner shaft slows down. When this happens, the pinion gears will start turning o
29、n their shafts. They will walk around the slower shaft and speed up the other shaft. This walking causes the outer shaft to rotate faster than the differenfial case, allowing the pinion shaft on the outerside to slide down its ramp. This releases the pressure on the outer clutches and lets the diffe
30、rential unit operate much like the standard model. It shows differential action when one axle is moving faster than the other. Note that the slower moving axle is receiving most of the torque since it remains clutched to the case. This type of differential will provide better traction than the stand
31、ard differential. It is particularly useful when roads are slippery and is also valuable in producing fast acceleration. A high-powered engine will often cause one wheel to spin during acceleration when using a standard differential. A somewhat different traction differential, uses cone clutches und
32、er coil spring pressure. A cross-sectional view is pictured in Drive Axle AssembilesThe Oldsmobile Anti-Spin differential, uses the pressure of the coil springs to force the clutch cones into tight engagement with the case. This action tends to lock the axles to the case. In order for differential a
33、ction to occur, the cones must be forced to slip. If one wheel slips, the other will still receive some driving force via the cone. The Positive-Traction differential in functions in a similar manner. Another positraction differential is illustrated i. Construction is similar to that in Figs16-19 an
34、d 16-20 except disc clutches are employed instead of cone clutch.HYPOID GEARING To facilitate lowering the propeller shaft tunnel in the floor of the car, and to allow lowering the body of the car, many ring gear pinion gears enter and drive the ring gear somewhat below the centerline of the axles.T
35、his gearing setup, using a modified spiral bevel gear, is referred to as HYPOID gearing. A special hypoid lubricant is necessary to prevent premature wear due to the sliding, wiping action that takes place between the ring and pinion gear teeth. Study the construction used in the pinion shaft assemb
36、ly. Take note of the two tapered roller bearings used to support the shaft. This type of bearing withstands both radial (forces working at right angles to the shaft) and longitudinal (lengthwise) thrust.SPIRAL BEVEL GEARING Another type of ring and pinion gearing uses the spiral bevel gear. This typ
37、e of pinion gear meshes with the ring gear at the axle centerline. The spiral tooth shape allows an overlapping tooth contact that makes for quiet operation, as well as added strength. Before one tooth rolls out of contact with another, a new tooth contact is made. This distributes the torque load o
38、ver several teeth. The cross section, shows the path of the churning lubricant (see arrows). Notice how it is thrown up and forward where it drops down and flows back, lubricating the ring gear and pinion gear, pinion bearings, etc.SPUR BEVEL More antiquated, as far as differential gearing is concer
39、ned, is the spur bevel. Auto Mechanics FundamentalsRING AND PINION The tooth contact position, as well as clearance and back lash (distance one gear will move back and forth Without moving the other gear), is of critical importance. Ring and pinions are always matched, and must be installed as a pai
40、r. NEVER REPLACE ONE WITHOUT THE OTHER. illustrates tooth clearance, backlash, as well as other gear tooth nomenclature. Correct and incorrect ring and pinion tooth contact patterns are shown in Fig. 16-28. The correct contact pattern is very important for strength, wear, and quiet operation. These
41、patterns are brought out by coating the teeth (after cleaning) with Prussian blue or white lead compound. The gears are revolved in both directions, and contact pattern becomes visible. The drive side is side that contacts when the pinion is driving the ring. The coast pattern is when the ring is dr
42、iving the pinion.译文 驱动桥在学习本章之后，你将了解不同类型驱动桥的组成，并能列举不同种类的驱动桥；比较后桥与前桥的不同之处；描述驱动桥的工作原理。驱动桥有很多重要作用。它可以使车轮回正，控制车轮滚动，可以使其中一个车轮的转速比另外一个车轮快，两个车轮均可获得转矩。驱动桥可以获得来自于车轮的反作用力，通过弹簧，操纵杆等将作用力传到车架上。驱动桥在车轮制动器被安装的基础上通过弹簧来固定，并获得簧上质量。很显然，驱动桥需要使用高质量的材料来制作。结构后桥的几个基本组成部分：桥壳，半轴，差速器。桥壳桥壳通常是由钢板模压件焊接在一起而制成的。桥壳的中心部分是由铸钢制成的。有两种类型的
43、桥壳常被使用：整体式桥壳（应用广泛）和分段式桥壳（应用较少）是由两个或者更多的部分组成。车桥两个车桥在桥壳的内部，它们在内部相接触，在某些位置它们是不接触的。外部的凸出端附在车轮和轮毂上。内部端被花键固定在差速器上，外端被滚子轴承所固定。连接轮两种方法被应用于驱动桥的轮毂上。一种方法是在驱动桥一端用拔销来固定，另一端通过凸缘固定。半轴的类型半轴有三种基本的类型，全浮式， 3/4浮式和半浮式。大多是汽车采用半浮式，大部分货车采用全浮式半轴支承。如果半轴折断，车轮将停止转动。驱动桥汽车转弯时的工况与普通行驶时的不同，必须使用一个叫做差速器的单元使两个半轴都获得动力，让左右驱动车轮的行驶速度不同。差
44、速器每个半轴的一侧都有齿轮，两半轴齿轮可以自由运动。可以看到差速器壳，它会绕着半轴上的齿轮转动。差速器壳上通过销连接齿圈和轴。差速器壳体会随着差速器转动，传动轴与主动齿轮轴相连接。当传动轴使主动齿轮轴转动时，齿圈也会随之转动。齿圈会绕着差速器壳体和十字轴转动。差速器的运动传动轴使主动齿轮轴转动，齿圈也会随之转动。当差速器壳体转动，十字轴随之转动。当差速器上的行星齿轮被安装在这个轴上时，它们会随着差速器壳体运动。 当汽车沿着直线方向行驶时，齿圈会绕着差速器壳体旋转。差速器行星齿轮和半轴齿轮绕着差速器壳体转动，轮齿之间无干涉。整个运动过程象一个固体单元。当汽车转弯时，差速器壳体继续旋转，推动行星齿
45、轮绕着轴转动。当要求车轮快速转动时，外部半轴齿轮的转速高于内部半轴齿轮。行星齿轮不仅仅是推动半轴齿轮转动，也使它们的轴转动。这可以使两个半轴齿轮同时绕着其各自的轴转动/图A中，汽车沿直线行驶，行星齿轮推动两个半轴齿轮转动。在图B中，右侧半轴齿轮的转速大于左侧半轴齿轮的转速。行星齿轮仍以相同的速度转动，仍然推动两个半轴齿轮转动，也推动轴的转动。这种运动会使右侧半轴齿轮的转速提高，从而超过十字轴的转速。相反的运动形式会使左侧半轴齿轮的转速降低。差速器的这种运动形式可以调节其自身以及驱动桥的转速变化。如果一个车轮开始打滑，驱动桥静止不动。差速器壳体继续旋转，驱动桥齿轮静止不动， 可以增加驱动桥的转矩
46、。一种有特殊结构的差速器将在后面的章节做介绍。差速器壳和差速器壳轴承一个质量大而且坚固的部分被安装在桥壳内，它包括行星齿轮，十字轴和轴承，称之为差速器壳。其内部装有两个大的轴承，称之为差速器壳轴承。差速器壳是桥壳的一部分。桥壳的组成部分包括半轴和差速器特殊结构的差速器为了避免动力的流失，车轮开始打滑时，特殊的差速器可以改变车轮的转矩而避免车轮打滑。这样可以使汽车原有的运动状态保持不变。尽管存在着很多的变化，但可采用摩擦装置来实现正常运动。克莱斯勒高牵引力差速器克莱斯勒高牵引力差速器是一个标准模型，有很多重要的附加条件半轴齿轮不是由两个差速器行星齿轮驱动的，而是由四个差速器行星齿轮驱动的。这就需
47、要两个分离的十字轴，两个轴之间的运动是相互独立的。轴的外端不是圆的而是平的，象V型。差速器壳体呈斜坡状。半轴齿轮上装有四个离合器盘，其中的两个离合器盘绕着差速器壳体转动，另外两个绕着止推部分转动。止推部分绕着半轴旋转，离合器盘运动到一起。高牵引力差速器的运动两个半轴的转速相同。当传动轴驱动行星齿轮转动时，转矩被传递到齿圈上。正如齿圈可以驱动差速器壳体一样，十字轴绕着差速器壳体转动。半轴齿轮随着差速器小齿轮转动。十字轴驱动小齿轮转动。两个十字轮轴被置于不同的位置上。这种滑动使轴向外边的方向运动。每个轴都向外运动，从而使轴上的行星齿轮向相同的方向运动，使离合器被锁住。这是汽车沿直线行驶的运动规律。
48、半轴转速不同当汽车转弯时，其内部轴的转速降低。当发生这种情况时，行星齿轮会使它的轴开始转动。一个轴的转速比较慢，另外一个轴的转速加快。这样会使外部轴的转速高于差速器壳体的转速，使外部齿轮轴产生滑动。所释放的压力使差速器的运动同标准模型一致。如所示差速器的一个半轴的转速高于另外一个半轴的转速。转速较慢的半轴可以获得大部分的转矩。这种差速器优于普通的差速器。当道路光滑的条件下，可以提高速度。功率较高的发动机通常选用标准型差速器。不同类型的差速器。在弹簧线圈压力下的锥形离合器。通过弹簧线圈而使锥形离合器安装在差速器壳体内。为了实现差速器的运动，需要使锥形离合器产生滑动。如果一个车轮产生滑动，另外一个车轮仍然可以通过弹簧线圈获得动力。准双曲面齿轮式差速器为了使汽车地板下传动轴的高度降低，车身高度降低，半轴上装有很多小齿轮。这种差速器的建立，通过螺旋锥齿轮传动，运动形式同准双曲面齿轮相同。使用准双曲面锥齿轮用极压润滑剂防止滑动是必要的。运动发生在齿圈和轮齿上。学习小齿轮轴结构的应用。注意观察两个滚子轴承对轴的支承作用。这种轴承起着止推作用。螺旋锥齿轮传动另外一种类型的小齿轮传动装置采用螺旋锥齿轮传动。这种类型的小齿轮与半轴中心的齿圈相配合。螺旋齿可以增强受力。很多轮齿会承受转矩。直齿锥齿轮差速器的齿轮也