Unit8 Automotive Steering System,Part I Technical and Practical Reading,Passage A Types of Steering System,The steering system is a major part of the car. A good steering system makes driving much more pleasurable, comfortable and safer. The steering system, including steering wheel, steering gears, linkages and other components, is used to control the direction of a cars motion.,Today, there are two basic types of steering systems: (1) recirculating ball steering and (2) rack and pinion steering. The recirculating ball steering can be either power-assisted or non-power. Rack and pinion is almost always power-assisted. See figure 8-1.,Figure 8-1,Recirulating Ball Steering,Recirculatingball steering is used on many trucks and SUVs today. The larger and heavier the automobile is, the more difficult it is to steer. Most large automobiles are equipped with a recirculatingball steering gear.,This type of steering gear is very low in friction and provides a good mechanical advantage for a heavy vehicle. The recirculating ball steering uses a series of links and arms to ensure both wheels turning in the same direction at the same time. See figure 8-2.,Figure 8-2,The recirculatingball steering system consists of steering wheel, steering shaft (column), worm gear and sector gear in a steering gear box, pitman arm, track rod, tie rod and steering arm. See figure 8-3.,Figure 8-3,The steering wheel is connected to the steering box through the steering shaft. On the end of the steering shaft is a worm gear in the steering box. And a ball nut rides on the worm gear and also engages with the sector gear on the pitman shaft. A pitman shaft is mounted in the box in a position 90 to the worm gear. See figure 8-4.,Figure 8-4,The pitman arm is connected to one end of the track rod. In the other end of the track rod is an idler arm. Between the idler and pitman arms, the track rod is supported in the proper position to keep the left and right wheels working together.,The inner tie rod ends are attached to either end of the track rod and provide pivot points for the steering gear. From there they go to the outer tie rod ends through an adjustment sleeve.,This sleeve joins the inner and outer tie rod ends together and allows for adjustment when the front wheels are aligned. The outer tie rod ends are connected to the steering knuckle arms that actually turn the front wheels. See figure 8-5.,Rack and Pinion Steering,Many modern cars use rack and pinion steering mechanisms. The advantage of rack and pinion steering is relatively simple and the cost is low. And it has a much better direct steering feel for the driver. By reducing the number of parts and pivot points, it can more accurately control wheel direction, making the steering more responsive. See figure 8-6.,Figure 8-6 Rack and Pinion Steering,The rack and pinion steering system consists of steering wheel, steering shaft, rack and pinion gear, tie rod and steering knuckle arm. In the rack and pinion steering, the steering wheel, through the steering shaft, is directly connected to a pinion gear that is in mesh with the the rack.,The rack is a long, toothed bar, which is attached to each end with the inner tie rod ends. The outer tie rod ends are attached to the steering knuckle arms. See figure 8-7.,Figure 8-7,When you turn the steering wheel, the pinion gear turns, causing the rack to move from left to right. This movement, in turn, via tie rods and the steering knuckle arms makes the front wheels steer.,Rack and pinion steering is almost always used with a McPherson strut suspension system. The bottom of the steering knuckle still pivots on a lower ball joint, but the top of the knuckle is connected to the strut assembly. In this system, the outer tie rod end is connected to the steering arm on the strut housing itself. See figure 8-8.,Figurte 8-8,New Words,pleasurable plerbl a. 令人愉快的 comfortable kmftbl a. 舒适的，舒服的 linkage liki n. 连合，转向拉杆 steer sti v. 驾驶，航行，转向 ensure inu v. 确定，保证，确保 pitman pitmn n. 摇杆，联接杆,sector sekt n. 扇形齿，齿扇 nut nt n. 螺母 sleeve sli:v n. 套筒 responsive rispnsiv a. 敏感的，响应度，响应性 toothed tu:t a. 有齿的，锯齿的，锯齿状的 pivot pivt v. 转动,Phrases and Expressions,steering system 转向系统，转向系 steering gear 转向装置（转向齿轮机构，转向器，操舷装置） steering gear box 转向齿轮箱 steering wheel 转向盘，驾驶盘 SUV (Sport Utility Vehicle) 运动型多用途车 recirculatingball steering 循环球式转向器,recirculating ball steering gear 循环球式转向器 mechanical advantage 机械利益，机械增益，机械效益 ball nut 转向循环球螺母 rack-and-pinion steering 齿轮齿条转向器 steering column 转向柱 worm gear 蜗轮传动装置，蜗杆齿轮,pitman arm 转向摇臂，转向臂 track rod 系杆，横杆，转向横拉杆 steering arm 转向操纵杆，转向臂，转向摇臂 steering shaft 转向轴 pitman shaft 连接杆轴，转向摇臂轴，连接轴 idler arm 随动臂，空转轮臂，空转臂,tie rod 转向横拉杆 inner tie rod end 转向横拉杆内端 outer tie rod end 转向横拉杆外端 steering knuckle arm 转向节臂 pivot point 支点 toothed bar 齿条，齿杆,EXERCISE 1,Mark the following statements with T (True) or F (False) according to the passage.,EXERCISE 2,Translate the following