附 錄 附錄 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. 附錄 B 懸架與轉(zhuǎn)向系統(tǒng) -懸架與轉(zhuǎn)向系統(tǒng)的基本組成與類(lèi)型 1.懸架系統(tǒng) 如果將一輛汽車(chē)的車(chē)橋直接固定到車(chē)架或車(chē)身上，道路上的每個(gè)凹凸不平的點(diǎn)都會(huì)將一個(gè)沖擊力傳遞給車(chē)輛。乘客會(huì)覺(jué)得不舒適，高速操縱極為困難。現(xiàn)代汽 車(chē)乘坐舒適、操控性好就是懸架系統(tǒng)的直接作用結(jié)果。 盡管輪胎和車(chē)輪必須隨著道路的凹凸不平而上、下跳動(dòng)，但對(duì)車(chē)身的影響應(yīng)盡可能小。采用任何一種懸架系統(tǒng)的目的都是允許車(chē)身向前移動(dòng)，而將上、下運(yùn)動(dòng)減到最小程度。懸架還應(yīng)允許汽車(chē)轉(zhuǎn)彎，但不能有過(guò)大的車(chē)身橫搖或輪胎側(cè)滑。 2.懸架系統(tǒng)的組成 1）車(chē)架 汽車(chē)的車(chē)架或車(chē)身應(yīng)為懸架系統(tǒng)形成一個(gè)剛性結(jié)構(gòu)基礎(chǔ)，并未該系統(tǒng)提供堅(jiān)固的錨固點(diǎn)。今天常見(jiàn)的車(chē)身結(jié)構(gòu)有兩種：車(chē)身在車(chē)架上的結(jié)構(gòu)（非承載式車(chē)身）和整體式結(jié)構(gòu)（承載式車(chē)身）。前者采用了單獨(dú)的鋼車(chē)架，車(chē)身的各個(gè)點(diǎn)通過(guò)連接螺栓固定到車(chē) 架上；后者的車(chē)身各部分均用作結(jié)構(gòu)件。承載式車(chē)身結(jié)構(gòu)最常見(jiàn)，而非承載式仍然用在皮卡及大型轎車(chē)上。 2）彈簧 彈簧是懸架系統(tǒng)的最明顯的部分。每輛汽車(chē)在其車(chē)架或車(chē)身與車(chē)橋之間都有某種彈簧。今天，使用的彈簧有三種：鋼板彈簧、螺旋彈簧和扭桿彈簧。一輛汽車(chē)可以使用兩種不同的彈簧。空氣彈簧一度用來(lái)替代其他的彈簧，但現(xiàn)在已經(jīng)過(guò)時(shí)。許多現(xiàn)代汽車(chē)都采用空氣懸架，但它們只是用于對(duì)彈簧的補(bǔ)充。 3）減振器 當(dāng)汽車(chē)在一水平路面上向前行駛，并且車(chē)輪碾壓到道路上的凸起時(shí)，懸架系統(tǒng)的彈簧就會(huì)快速壓縮（螺旋彈簧）或者扭轉(zhuǎn)（鋼板彈簧和扭桿彈簧 ）。彈簧試圖返回到原來(lái)的正常安裝位置。因此，彈簧回彈，使車(chē)身抬高。由于彈簧已經(jīng)存儲(chǔ)了能量，所以彈簧的回彈會(huì)超過(guò)其正常長(zhǎng)度范圍。汽車(chē)的向上跳躍運(yùn)動(dòng)也將有助于彈簧的回彈超過(guò)彈簧的正常長(zhǎng)度范圍。 彈簧回彈之后，汽車(chē)的重量將使彈簧壓縮。由于汽車(chē)向下運(yùn)動(dòng)，下行的車(chē)身所積累的能量將推動(dòng)壓縮彈簧，使其高度低于正常的安裝高度。這就導(dǎo)致了彈簧的再次回彈。這個(gè)過(guò)程（叫做彈簧震蕩）逐漸減弱，直至汽車(chē)最后靜止為止。彈簧的震蕩會(huì)影響操縱性和乘坐舒適性，因而必須加以控制。 4）空氣減振器 有些懸架系統(tǒng)采用兩個(gè)可調(diào)的空氣減振器，這兩個(gè)減 振器安裝在后懸架上，并且用軟管連接到空氣閥上。 空氣減振器采用液壓減振系統(tǒng)，其工作方式與普通減振器相同。此外，空氣減振器內(nèi)還有密閉的空氣室，空氣室的氣壓與來(lái)自高度控制傳感器的壓力相互作用。改變到空氣室的壓力就會(huì)引起減振器長(zhǎng)度即工作范圍的增、減。 通過(guò)塑料管將壓縮空氣輸送到空氣減振器。此管將減振器與空氣閥相連。用于升高減振器的壓縮空氣一般取自外部氣源（如維修站壓縮機(jī)），并通過(guò)空氣閥進(jìn)入。為了將不需要的空氣從減振器放掉（降低汽車(chē)高度），要壓下空氣閥芯，使空氣放出。 5）懸架擺臂 所有的汽車(chē)都有或擺臂或滑柱，以便 保持車(chē)輪總成處于正確的位置。擺臂與滑柱可讓車(chē)輪上、下移動(dòng)，同時(shí)阻止其他方向的運(yùn)動(dòng)。在汽車(chē)加速、制動(dòng)或轉(zhuǎn)彎時(shí)，車(chē)輪往往會(huì)產(chǎn)生不希望有的運(yùn)動(dòng)。汽車(chē)懸架可以只有擺臂，或者將擺臂與滑柱結(jié)合使用。 3.懸架的類(lèi)型 1）前懸架系統(tǒng) 幾乎所有的前懸架系統(tǒng)都是獨(dú)立懸架。采用獨(dú)立懸架，每個(gè)前輪都能自由地上、下運(yùn)動(dòng)，對(duì)其他的車(chē)輪影響最小。在獨(dú)立懸架系統(tǒng)中，加給車(chē)架的扭轉(zhuǎn)作用要遠(yuǎn)遠(yuǎn)小于采用整體式車(chē)橋的懸架系統(tǒng)。然而，一些非道路四輪驅(qū)動(dòng)車(chē)輛和大型貨車(chē)仍然采用整體式車(chē)橋前懸架。兩種主要的獨(dú)立前懸架是傳統(tǒng)式獨(dú)立前懸架麥弗遜滑柱式獨(dú)立前 懸架。 （ 1）傳統(tǒng)式獨(dú)立前懸架 在傳統(tǒng)式獨(dú)立前懸架中，每個(gè)車(chē)輪采用一個(gè)或兩個(gè)擺臂。在大多數(shù)系統(tǒng)中，螺旋彈簧安裝在車(chē)架與下擺臂之間。而在老式懸架系統(tǒng)中，螺旋彈簧安裝在上擺臂與車(chē)身之間。在扭桿彈簧前懸架中，下擺臂上移，從而使扭桿彈簧發(fā)生扭轉(zhuǎn)變形。 （ 2）螺旋彈簧獨(dú)立前懸架 一種采用橡膠軸套擺臂支軸的典型的獨(dú)立前懸架。螺旋彈簧的頂部置入一個(gè)杯形件中，并且頂靠在車(chē)架上。螺旋彈簧的底部支撐在下擺臂上的彈簧襯墊上。每個(gè)減振器的頂部都固定到車(chē)架上，底部都固定到下擺臂上。 當(dāng)車(chē)輪碰到道路上的凸起部位時(shí)，車(chē)輪就會(huì)被向上頂起。 這就使擺臂繞支軸向上轉(zhuǎn)動(dòng)，從而使彈簧和減振器被壓縮。橡膠緩沖墊限制擺臂的最大行程，并在到達(dá)極限位置時(shí)，對(duì)擺臂的運(yùn)動(dòng)起到緩沖作用。對(duì)于轉(zhuǎn)向系統(tǒng)而言，前輪轉(zhuǎn)向節(jié)繞球形接頭轉(zhuǎn)動(dòng)。 （ 3）扭桿