contact the drum by hydraulic cylinders or a mechanical linkage. 这种制动器有两个固定在制动底板上的制动蹄，通过液压轮缸或机械杆系作用从内侧向外推开与制动鼓接触。
5) Exposed to the air, disc brakes radiate the heat to the air better than drum brakes: This
means that the brake can be operated continuously for a longer period, i.e. they have a greater resistance to fade (fall-off in brake efficiency due to heat).
由于暴露于空气中，盘式制动器的散热效果比鼓式的要好：这意味着盘式制动器能持续 使用更长的时间，也就是说其抗热衰退性（因受热导致制动效能下降）要好得多。 6) An advantage of disc brakes in comparison to drum brakes: ① Better braking efficiency 制动效能更好
② Equal wear of the inboard and outboard brake pads内侧和外侧制动盘等磨损 ③ Brake noise is better suppressed 更好地抑制制动噪声
④ Relatively constant brake factor performance with lower susceptibility to fading
相对稳定的制动性能，衰减因子较低 Disadvantage ：
1) Short brake pad life when used on heavy-duty commercial vehicles 制动块在重型商用车辆使用时寿命较低
2) Higher acquisition and operating costs 较高的成本
7) The master cylinder contains two separate sections, there is a piston in each section and
both pistons are connected to a brake pedal in the driver's compartment. P107
制动主缸由两个分开的部分组成，每个部分都有一个活塞，两个活塞都与驾驶室里的制动踏板相连接。
8) The function of an anti-lock or anti-skid, braking system is to prevent the wheels from
locking under hard braking. Maximum braking force is obtained just before the wheels lock and skid. Such anti-skid systems are useful on slippery surfaces, such as ice and snow, where the wheels may lock easily. P112
防抱死制动系统的作用是防止在强制动条件下车轮抱死。只在车轮抱死拖滑时才会获得最大制动力。这类防滑系统在冰、雪等光滑路面非常实用，因为在这些路面上车轮容易抱死。 9) The wheel-speed sensor monitors the motion of the wheel. If one wheel shows signs of
locking, there is a sharp rise in peripheral wheel deceleration and in wheel slip. If these exceed defined critical values, the controller sends commands to the solenoid-valve unit to stop or reduce the buildup of wheel-brake pressure until the danger of lock-up has passed. The brake pressure must then be built up again in order to ensure that the wheel is not under-braked.
轮速传感器监控着车轮的运动，如果一个车轮出现抱死信号，也就是外车轮减速度急剧增大且车轮开始滑动．如果超出临界值，控制器给电磁阀发送命令来停止或降低制动压力，直到抱死的危险消除．然后制动力再增大确保车轮制动力不会不足．
10) A separate frame must be light yet strong enough to resist the various loads and road forces.
Commercial vehicles normally use a separate steel frame to provide the rigidity needed to support the various loads. The two long side members of channel section are riveted to a number of cross members to give a low weight frame which offers great resistance to bending, twisting. P126
分离式车架必须足够轻巧而且结实，以承受变化的载荷和路面作用力。商用车通常使用分离式钢质车架，以获得较好的刚度来承受变化的载荷。两根槽形的长纵梁铆接着很多横梁，这使车架重量较轻，具有较好的抗弯和抗扭能力。
11) Most cars use a unitized body construction, a combined body and frame. Unitized body
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construction is lighter than body/frame construction, but noisier. Rubber mounts are used between the body section and mechanical parts to absorb vibrations. The floor pan is made of sections that support the rear suspension and the transmission.
多数轿车采用承载式车身，也就是车身和车架融为一体。承载式车身比非承载式车身质量轻，但噪声大。在车身和机械部件之间安装橡胶块以吸收振动。地板由一些支撑后悬架和变速器的部件组成。
第五章 悬架系统
1) The basic steering system in most cars is the same. The steering gear of steering box is the
heart of the steering system. This usually is next to the engine. A shaft extends from the back of the steering gear. This shaft is connected to the steering column or steering shaft. The steering wheel is at the top of the steering column. Another shaft comes from the bottom of the steering gear. This shaft connects to the arms, rods, and links. This parts assembly, called the steering linkage, connects the steering gear to the parts at the wheels. The wheels and tires mount to the steering knuckles. As shown in Fig. 5-1, the knuckles are pivoted at the top and bottom. Thus, the wheels and tires can turn from side to side. P132 多数汽车的转向系基本上是一样的。转向系的核心是转向器，一般位于发动机附近。一根轴从转向器后部伸出，连接着转向柱。方向盘在转向柱的顶端。另一根轴从转向器低端伸出，连接着转向臂、转向拉杆和转向杆系，这些部件总称为转向传动机构，连接转向器和车轮上的部件。车轮和轮胎安装在转向节上。如图5-1所示，转向节的上下端可自由转动，这样车轮可从一侧转到另一侧。
2) While the steering system may look complicated, it works quite simply. When a driver
drives a car straight down the road, the steering gear is centered. The gear holds the linkage centered so that the wheels and tires point straight ahead. When the driver turns the steering wheel, the steering shaft rotates and the steering gear moves toward that side. The shaft coming out the bottom of the steering gear turns, as well. When the shaft turns, it pulls the linkage to one side and makes the steering knuckles turn slightly about their pivot points. Thus, the steering knuckle, spindle, wheels, and tires turn to one side, causing the car to turn.
转向系看起来复杂，工作原理却很简单。汽车直行时，转向器处于中间位置，转向传动机构也处于中间位置，车轮直行。驾驶员转动方向盘，转向轴旋转，转向器向同侧转动，同时转向器底部的输出轴也会旋转。输出轴转动时，会向一侧拉动拉杆，使得转向节绕其支点旋转。这样，转向节、转向节轴端、车轮和轮胎都
3) Most heavy commercial vehicles use the recirculating ball type of steering gear. This
steering gear is durable, with good steering response and good road feel for the driver. P135 多数重型商用车采用循环球式转向器，这类转向器性能稳定、转向灵敏而且路感好。 4) In the recirculating ball steering gear, the wormshaft is the input shaft. The wormshaft
connects to the steering column in such a way that a mechanic can remove the steering gear or steering column independently of one another. The sector shaft (also called the pitman shaft) is like the output shaft of the steering gear. The main parts of the steering gear are the balls, ball nut, and the gear teeth on the ball nut.
在循环球式转向器中，转向螺杆是输入轴。这样转向螺杆连接着转向柱，修理工就可独立拆卸转向器或转向柱。齿扇轴（也叫摇臂轴）相当于转向器的输出轴．转向器的主要部件是钢球，转向螺母和转向螺母上的齿．
5) As the wormshaft turns, the balls move the ball nut up and down along the wormshaft. This
turns the sector shaft, since the sector teeth mesh with the ball nut teeth. The sector shaft is
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connected through steering linkage to the front wheels.
当转向螺杆转动时，刚球使球螺母沿转向螺杆上下运动．由于扇齿与球螺母齿啮合，齿扇轴转动．齿扇轴通过转向传动机构与前轮连接．
6) The rack-and-pinion system has two main parts－the pinion and the rack. The pinion is on
the end of the steering column. The steering wheel turns the pinion. The rack is a long, flat bar with teeth on one side. The rack teeth mesh with the teeth on the pinion.
齿轮齿条转向器有两个主要部件－齿轮和齿条．齿轮安装在转向柱的末端．转向盘转动齿轮．齿条是一个一面有齿长平杆．齿条与齿轮啮合．
7) Rack-and-pinion steering is used on many new smaller cars and on most cars with a
transverse engine. This steering gear is small and lightweight. It provides good steering with minimum driver effort. Also, rack-and-pinion steering needs fewer parts in the steering gear and linkage. Thus, it is easy to service. Rack-and- pinion steering gives more feedback and road feel to the driver.
很多新型小汽车和多数发动机横置的汽车都采用齿轮齿条式转向器。这类转向器尺寸小、重量轻，而且转向轻便。另外，转向器和转向传动机构所需的部件较少，便于维修。齿轮齿条式转向器为驾驶员提供了较好的反馈和路感．
8) The suspension covers the arrangement used to connect the wheels to the body.The purpose
is to prevent large shocks, caused by the wheels striking bumps in the road, being passed to the vehicle occupants and components; otherwise discomfort and damage would occur. P 悬架是车架（车身）与车桥（车轮）之间一切连接传力装置的总称。其目的是防止车轮遇到路面不平产生的巨大冲击传给车内的货物和乘客；否则会产生不舒适的感觉和货物的损坏。
9) The suspension system has two subsystems－the front suspension and the rear suspension.
The front suspension is more complicated than the rear suspension. This is because the front wheels must move in several different directions. The wheels must move up and down with the suspension and turn left to right with the steering. Since the car goes in the direction in which thefront wheels point, the alignment of the front wheels is important.
悬架系统有两个子系统－前悬架和后悬架．前悬架比后悬架复杂．这是因为前轮需要在不同方向运动．车轮必须随悬架上下运动并随转向系统左右转动．因为汽车在前轮指向的方向上行驶，所以前轮定位很重要．
10) Toe-in specifies the degree to which non-parallel front wheels are closer together at the
front than at the rear; measured at the edges of the rims at the wheel center height. 车轮前束指定了不平行前轮前边缘比后边缘近的程度；这在车轮中部边缘处测得．
11) The kingpin angle is the inclination of the steering axis (kingpin) relative to the longitudinal
plane, measured in the transverse plane of the vehicle.
主销内倾角是转向轴（主销）相对于纵向平面的倾斜，在汽车横向平面内测得．
12) Camber is the inclination of the wheel relative to the longitudinal vehicle plane, measured
in the transverse plane of the vehicle. Positive camber means that the wheels are tilted further out at the top than at the bottom.
车轮倾角是车轮在纵向平面的倾斜，在汽车的横向平面内测得．车轮外倾角指车轮顶部比底部更向外倾斜．
13) Caster is specified as the angle by which the steering axis ( kingpin line ) deviates from the
vertical when viewed from the side, or as that distance on the road surface by which the wheel contact point trails the point at which an extension of the steering axis meets the road surface.
主销后倾特指从车辆侧面观察时，转向轴（主销）偏离垂直方向的角度，或车轮和路面接
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触点与主销延长线与路面交点间的距离．
14) List the main functions of tire:
1) Absorb shocks resulting from irregularities in the road. 吸收来自不规则路面的振动．
2) Provide frictional contact between the wheels and the road so that good traction is
secured. This permits the transmitting of power through the tires to the road for rapid accelerating, combats the tendency of the car to skid on turns and allows quick stops when the brakes are applied.
提供车轮与路面之间摩擦接触，保证汽车稳定行驶．这可使汽车突 然加速时传递驱动力，在汽车转弯时避免打滑，刹车时快速停车．
3) There are two basic types of tires－those with inner tubes and those without (called
“tubeless” tires). Most modern automobile tires are of the tubeless type. Truck and bus tires are usually of the tube type.
轮胎有两种基本类型－有内胎轮胎和无内胎轮胎．大多数现代汽车轮胎是无内胎的．卡车和公共汽车轮胎一般是有内胎的．
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