外文翻译--悬架与转向系统-悬架与转向系统的基本组成与类型

附 录 附录 A Basic Parts and Types of the Suspension and Steering Systems Suspension System If a vehicles axles were bolted directly to its frame or body, every rough spot in the road would transmit a jarring force throughout the vehicle. Riding would be uncomfortable, and handling at freeway speeds would be impossible. The fact that the modern vehicle rides and handles well is a direct result of a suspension system. Even though the tires and wheels must follow the road contour, the body should be influenced as little as possible 1. The purpose of any suspension system is to allow the body of the vehicle to travel forward with a minimum amount of up-and-down movement. The suspension should also permit the vehicle to make turns without excessive body roll or tire skidding. Suspension System Components Vehicle Frame A vehicles frame or body must form a rigid structural foundation and provide solid anchorage points for the suspension system. There are two types of vehicle construction in common use today: body-over-frame construction, which uses a separate steel frame to which the body is bolted at various points and unibody construction, in which the body sections serve as structural members. Unibody construction is the most common, but body-over-frame construction is still used on pickup trucks and large cars. Springs The springs are the most obvious part of the suspension system. Every vehicle has a spring of some kind between the frame or body and the axles. There are three types of springs in general use today: leaf spring, coil spring, and torsion bar. Two different types of springs can be used on one vehicle. Air springs were once used in place of the other types of springs, but are now obsolete. Many modern vehicles have air-operated suspensions, but they are used to supplement the springs. Shock Absorbers When the vehicle is traveling forward on a level surface and the wheels strike a bump, the spring is rapidly compressed (coil springs) or twisted (leaf springs and torsion bars). The spring will attempt to return to its normal loaded length. In so doing, it will rebound, causing the body of the vehicle to be lifted. Since the spring has stored energy, it will rebound past its normal length. The upward movement of the vehicle also assists in rebounding past the springs normal length. The weight of the vehicle then pushes the spring down after the spring rebounds. The weight of the vehicle will push the spring down, but since the vehicle is traveling downward, the energy built up by the descending body will push the spring below its normal loaded height. This causes the spring to rebound again. This process, called spring oscillation, gradually diminishes until the vehicle is finally still. Spring oscillation can affect handling and ride quality and must be controlled. Air Shock Absorbers Some suspension systems incorporate two adjustable air shock absorbers that are attached to the rear suspension and connected to an air valve with flexible tubing. Air operated shock absorbers have hydraulic dampening systems which operate in the same manner as those on conventional shocks. In addition, they contain a sealed air chamber, which is acted on by pressure from a height control sensor. Varying the pressure to the air chamber causes the air shock to increase or decrease its length or operating range. Air pressure is delivered to the air shocks through plastic tubing. The tubing connects the shocks to an air valve. Air pressure for raising the shocks is generally obtained from an outside source, such as a service station compressor, and is admitted through the air valve. To deplete the shocks of unwanted air (lower vehicle curb height), the air valve core is depressed, allowing air to escape. Control Arms All vehicles have either control arms or struts to keep the wheel assembly in the proper position. The control arms and struts allow the wheel to move up and down while preventing it from moving in any other direction. The wheel will tend to move in undesirable directions whenever the vehicle is accelerated, braked, or turned. Vehicle suspensions may have control arms only or a combination of control arms and struts. Types of the Suspension Front Suspension Systems Almost all modern front suspension systems are independent. With an independent suspension, each front wheel is free to move up and down with a minimum effect on the other wheel. In an independent suspension system, there is also far less twisting motion imposed on the frame than in a system with a solid axle. Nevertheless, a few off-road, four wheel drive vehicles and large trucks continue to use a solid axle front suspension. The two major types of independent front suspension are the conventional front suspension and the MacPherson strut front suspension. Conventional Front Suspension In the conventional front suspension system, one or two control arms are used at each wheel. In most systems, the coil springs are mounted between the vehicles frame and the lower control arm. In older systems, coil springs are mounted between the upper control arm and vehicle body. In a torsion bar front suspension system, the lower arm moves upward, it twists the torsion bar. Coil Spring Front Suspension Fig.11-1 shows a typical independent front suspension that uses rubber bushing control arm pivots. The top of the coil spring rests in a cup-like spot against the frame (unshown). The bottom of the coil spring is supported by a pad on the lower control arm. The top of each shock absorber is fastened to the frame； the bottom is attached to the lower control arm. Torsion Bar Front Suspension A torsion bar is located on each side of the frame in the front of the vehicle. The lower control arm is attached to the free end of the torsion bar. When the wheel is driven upward, the lower control arm moves upward, twisting the long spring steel bar. Macpherson Strut Front Suspension Most modern vehicles, especially those with front-wheel drive, use the MacPherson strut front suspension systems, Fig.11-2. Note that the MacPherson strut contains a coil spring, which is mounted on top of the heavy strut-and-pedestal assembly. The entire MacPherson strut assembly is attached to the steering knuckle at the lower part of the pedestal. The bottom of the MacPherson strut assembly is attached to the single control arm through a ball joint. The entire strut assembly turns when the wheel is turned. A bearing or thrust plate at the top of the strut assembly allows relative movement between the assembly and the vehicle body. The ball joint allows the strut assembly to turn in relation to the control arm. The strut contains a damper, which operates in the same manner as a conventional shock absorber. Most damper assemblies have a protective cover that keeps dirt and water away from the damper piston rod. The advantage of the MacPherson strut is its compact design, which allows more room for service on small car bodies. Solid Axle Front Suspension The use of the solid axle front suspension (or dependent suspension) is generally confined to trucks and off-road vehicles. This system uses a solid steel dead. Rear Suspension Systems Rear suspensions on vehicles with a solid rear axle housing generally utilize coil springs or leaf springs. When the vehicle has an independent rear suspension system, coil springs, MacPherson struts, a single transverse leaf spring, or even torsion bars can be used. Steering System The steering system is designed to allow the driver to move the front wheels to the right or left with a minimum of effort and without excessive movement of the steering wheel. Although the driver can move the wheels easily, road shocks are not transmitted to the driver. This absence of road shock transfer is referred to as the nonreversible feature of steering systems. The basic steering system can be divided into three main assemblies: The spindle and steering arm assemblies. The linkage assembly connecting the steering arms and steering gear. The steering wheel, steering shaft, and steering gear assembly. Steering Gear The steering gear is designed to multiply the drivers turning torque so the front wheels may be turned easily. When the parallelogram linkage is used, the torque developed by the driver is multiplied through gears and is then transmitted to the wheel spindle assemblies through the linkage. On the rack-and-pinion steering system, the steering shaft is connected directly to the pinion shaft. Turning the pinion moves the rack section, witch moves the linkage. Late-model vehicles use either manual steering gears or power steering gears. There are three types of the steering gears in use: recirculating ball steering gear, worm-and-roller steering gear and rack-and-pinion steering gear. Power Steering Power steering is designed to reduce the effort needed to turn the steering wheel by utilizing hydraulic pressure to bolster (strengthen) the normal torque developed by the steering gear. Power steering systems should ease steering wheel manipulation and, at the same time, offer enough resistance so that the driver can retain some road feel. Power steering is used with both conventional and rack-and-pinion systems (Fig.11-3). The self-contained steering gear contains the control valve mechanism, the power piston, and the gears. Pressure developed by the unit is applied to the pitman shaft The power rack-and-pinion steering system also uses a rotary control valve that directs the hydraulic fluid from the pump to either side of the rack piston. An overall view of this setup is shown in Figure 11-3. Steering wheel motion is transferred to the pinion. From there, it is sent through the pinion teeth, which are in mesh with the rack teeth. The integral rack piston, which is connected to the rack, changes hydraulic pressure to a linear force (back and forth movement in a straight line). This, in turn, moves the rack in a right or left direction. The force is transmitted by the inner and outer tie rods to the steering knuckles, which, in turn, move the wheels. 附录 B 悬架与转向系统 -悬架与转向系统的基本组成与类型 1.悬架系统 如果将一辆汽车的车桥直接固定到车架或车身上，道路上的每个凹凸不平的点都会将一个冲击力传递给车辆。乘客会觉得不舒适，高速操纵极为困难。现代汽 车乘坐舒适、操控性好就是悬架系统的直接作用结果。 尽管轮胎和车轮必须随着道路的凹凸不平而上、下跳动，但对车身的影响应尽可能小。采用任何一种悬架系统的目的都是允许车身向前移动，而将上、下运动减到最小程度。悬架还应允许汽车转弯，但不能有过大的车身横摇或轮胎侧滑。 2.悬架系统的组成 1）车架 汽车的车架或车身应为悬架系统形成一个刚性结构基础，并未该系统提供坚固的锚固点。今天常见的车身结构有两种：车身在车架上的结构（非承载式车身）和整体式结构（承载式车身）。前者采用了单独的钢车架，车身的各个点通过连接螺栓固定到车 架上；后者的车身各部分均用作结构件。承载式车身结构最常见，而非承载式仍然用在皮卡及大型轿车上。 2）弹簧 弹簧是悬架系统的最明显的部分。每辆汽车在其车架或车身与车桥之间都有某种弹簧。今天，使用的弹簧有三种：钢板弹簧、螺旋弹簧和扭杆弹簧。一辆汽车可以使用两种不同的弹簧。空气弹簧一度用来替代其他的弹簧，但现在已经过时。许多现代汽车都采用空气悬架，但它们只是用于对弹簧的补充。 3）减振器 当汽车在一水平路面上向前行驶，并且车轮碾压到道路上的凸起时，悬架系统的弹簧就会快速压缩（螺旋弹簧）或者扭转（钢板弹簧和扭杆弹簧 ）。弹簧试图返回到原来的正常安装位置。因此，弹簧回弹，使车身抬高。由于弹簧已经存储了能量，所以弹簧的回弹会超过其正常长度范围。汽车的向上跳跃运动也将有助于弹簧的回弹超过弹簧的正常长度范围。 弹簧回弹之后，汽车的重量将使弹簧压缩。由于汽车向下运动，下行的车身所积累的能量将推动压缩弹簧，使其高度低于正常的安装高度。这就导致了弹簧的再次回弹。这个过程（叫做弹簧震荡）逐渐减弱，直至汽车最后静止为止。弹簧的震荡会影响操纵性和乘坐舒适性，因而必须加以控制。 4）空气减振器 有些悬架系统采用两个可调的空气减振器，这两个减 振器安装在后悬架上，并且用软管连接到空气阀上。 空气减振器采用液压减振系统，其工作方式与普通减振器相同。此外，空气减振器内还有密闭的空气室，空气室的气压与来自高度控制传感器的压力相互作用。改变到空气室的压力就会引起减振器长度即工作范围的增、减。 通过塑料管将压缩空气输送到空气减振器。此管将减振器与空气阀相连。用于升高减振器的压缩空气一般取自外部气源（如维修站压缩机），并通过空气阀进入。为了将不需要的空气从减振器放掉（降低汽车高度），要压下空气阀芯，使空气放出。 5）悬架摆臂 所有的汽车都有或摆臂或滑柱，以便 保持车轮总成处于正确的位置。摆臂与滑柱可让车轮上、下移动，同时阻止其他方向的运动。在汽车加速、制动或转弯时，车轮往往会产生不希望有的运动。汽车悬架可以只有摆臂，或者将摆臂与滑柱结合使用。 3.悬架的类型 1）前悬架系统 几乎所有的前悬架系统都是独立悬架。采用独立悬架，每个前轮都能自由地上、下运动，对其他的车轮影响最小。在独立悬架系统中，加给车架的扭转作用要远远小于采用整体式车桥的悬架系统。然而，一些非道路四轮驱动车辆和大型货车仍然采用整体式车桥前悬架。两种主要的独立前悬架是传统式独立前悬架麦弗逊滑柱式独立前 悬架。 （ 1）传统式独立前悬架 在传统式独立前悬架中，每个车轮采用一个或两个摆臂。在大多数系统中，螺旋弹簧安装在车架与下摆臂之间。而在老式悬架系统中，螺旋弹簧安装在上摆臂与车身之间。在扭杆弹簧前悬架中，下摆臂上移，从而使扭杆弹簧发生扭转变形。 （ 2）螺旋弹簧独立前悬架 一种采用橡胶轴套摆臂支轴的典型的独立前悬架。螺旋弹簧的顶部置入一个杯形件中，并且顶靠在车架上。螺旋弹簧的底部支撑在下摆臂上的弹簧衬垫上。每个减振器的顶部都固定到车架上，底部都固定到下摆臂上。 当车轮碰到道路上的凸起部位时，车轮就会被向上顶起。 这就使摆臂绕支轴向上转动，从而使弹簧和减振器被压缩。橡胶缓冲垫限制摆臂的最大行程，并在到达极限位置时，对摆臂的运动起到缓冲作用。对于转向系统而言，前轮转向节绕球形接头转动。 （ 3）扭杆