外文翻譯--汽車轉向系統(tǒng)工作原路介紹

附錄 A How Car Steering Works by Karim Nice You know that when you turn the steering wheel in your car, the wheels turn. Cause and effect, right? But a lot of interesting stuff goes on between the steering wheel and the tires to make this happen. Up Next Car Suspension Quiz How Car Suspensions Work D: Rocket Shock Absorbers In this article, well see how the two most common types of car steering systems work: rack-and-pinion and recirculating-ball steering. Then well examine power steering and find out about some interesting future developments in steering systems, driven mostly by the need to increase the fuel efficiency of cars. But first, lets see what you have to do turn a car. Its not quite as simple as you might think! When it comes to crucial automotive systems, steering is right up there with the engine and the brakes. The inner workings of this important component are pretty cool. Turning the Car You might be surprised to learn that when you turn your car, your front wheels are not pointing in the same direction. For a car to turn smoothly, each wheel must follow a different circle. Since the inside wheel is following a circle with a smaller radius, it is actually making a tighter turn than the outside wheel. If you draw a line perpendicular to each wheel, the lines will intersect at the center point of the turn. The geometry of the steering linkage makes the inside wheel turn more than the outside wheel. There are a couple different types of steering gears. The most common are rack-and-pinion and recirculating ball. Rack-and-pinion Steering Rack-and-pinion steering is quickly becoming the most common type of steering on cars, small trucks and SUVs. It is actually a pretty simple mechanism. A rack-and-pinion gearset is enclosed in a metal tube, with each end of the rack protruding from the tube. A rod, called a tie rod, connects to each end of the rack. The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack. The tie rod at each end of the rack connects to the steering arm on the spindle (see diagram above). The rack-and-pinion gearset does two things: It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels. It provides a gear reduction, making it easier to turn the wheels. On most cars, it takes three to four complete revolutions of the steering wheel to make the wheels turn from lock to lock (from far left to far right). The steering ratio is the ratio of how far you turn the steering wheel to how far the wheels turn. For instance, if one complete revolution (360 degrees) of the steering wheel results in the wheels of the car turning 20 degrees, then the steering ratio is 360 divided by 20, or 18:1. A higher ratio means that you have to turn the steering wheel more to get the wheels to turn a given distance. However, less effort is required because of the higher gear ratio. Generally, lighter, sportier cars have lower steering ratios than larger cars and trucks. The lower ratio gives the steering a quicker response - you dont have to turn the steering wheel as much to get the wheels to turn a given distance - which is a desirable trait in sports cars. These smaller cars are light enough that even with the lower ratio, the effort required to turn the steering wheel is not excessive. Some cars have variable-ratio steering, which uses a rack-and-pinion gearset that has a different tooth pitch (number of teeth per inch) in the center than it has on the outside. This makes the car respond quickly when starting a turn (the rack is near the center), and also reduces effort near the wheels turning limits. Power Rack-and-pinion When the rack-and-pinion is in a power-steering system, the rack has a slightly different design. Part of the rack contains a cylinder with a piston in the middle. The piston is connected to the rack. There are two fluid ports, one on either side of the piston. Supplying higher-pressure fluid to one side of the piston forces the piston to move, which in turn moves the rack, providing the power assist. Well check out the components that provide the high-pressure fluid, as well as decide which side of the rack to supply it to, later in the article. First, lets take a look at another type of steering. Recirculating-ball Steering Recirculating-ball steering is used on many trucks and SUVs today. The linkage that turns the wheels is slightly different than on a rack-and-pinion system. The recirculating-ball steering gear contains a worm gear. You can image the gear in two parts. The first part is a block of metal with a threaded hole in it. This block has gear teeth cut into the outside of it, which engage a gear that moves the pitman arm (see diagram above). The steering wheel connects to a threaded rod, similar to a bolt, that sticks into the hole in the block. When the steering wheel turns, it turns the bolt. Instead of twisting further into the block the way a regular bolt would, this bolt is held fixed so that when it spins, it moves the block, which moves the gear that turns the wheels. Instead of the bolt directly engaging the threads in the block, all of the threads are filled with ball bearings that recirculate through the gear as it turns. The balls actually serve two purposes: First, they reduce friction and wear in the gear； second, they reduce slop in the gear. Slop would be felt when you change the direction of the steering wheel - without the balls in the steering gear, the teeth would come out of contact with each other for a moment, making the steering wheel feel loose. Power steering in a recirculating-ball system works similarly to a rack-and-pinion system. Assist is provided by supplying higher-pressure fluid to one side of the block. Now lets take a look at the other components that make up a power-steering system. Power Steering There are a couple of key components in power steering in addition to the rack-and-pinion or recirculating-ball mechanism. Pump The hydraulic power for the steering is provided by a rotary-vane pump (see diagram below). This pump is driven by the cars engine via a belt and pulley. It contains a set of retractable vanes that spin inside an oval chamber. As the vanes spin, they pull hydraulic fluid from the return line at low pressure and force it into the outlet at high pressure. The amount of flow provided by the pump depends on the cars engine speed. The pump must be designed to provide adequate flow when the engine is idling. As a result, the pump moves much more fluid than necessary when the engine is running at faster speeds. The pump contains a pressure-relief valve to make sure that the pressure does not get too high, especially at high engine speeds when so much fluid is being pumped. 附錄 B 汽車轉向系統(tǒng)工作原路介紹 Karim Nice 著 顯而易見，當你坐在車里轉動方向盤時。車輪會跟著運動。像一對因果關系，是吧？但是其中是有很多令人感興趣的部件在方向盤和輪胎之間運動才構成了我們以上看的原因和結果。 在這篇文章中，我們將看到兩種最 常見的轉向系統(tǒng)是如何工作的：齒輪齒條式轉向器和循環(huán)球式轉向器。然后我們會研究一下動力轉向并發(fā)現(xiàn)些令人欣喜的轉向系統(tǒng)未來發(fā)展動向，其中大部分是由提高汽車燃油效率驅使產生的。但是首先，讓我們看看你想讓一輛汽車轉向都需要做些什么。其中的過程可能并不像你想象的那么簡單。 當說到汽車行駛的關鍵系統(tǒng)時，轉向系統(tǒng)當然地成為和發(fā)動機系統(tǒng)，制動系統(tǒng)處于同樣重要的地位。這個至關重要的部分內部的工作過程也是相當激動人心的。 汽車的轉向 當 你控制汽車轉彎的時候你車的前輪并沒有只指向同一個方向，在了解到這些的時候你可能會很 奇怪。 要想讓汽車轉向平順，每個車輪就必須沿著不同的軌跡運動。因為內側輪胎是沿著較小半徑的圓周軌跡運動的。如果沿著每個車輪做一條垂直線，這些線會相交于轉向軌跡的中心點。轉向系統(tǒng)聯(lián)動裝置的幾何學特性使得內側車輪轉向角度比外側車輪大些。 通常是有好幾種不同類型的轉向齒輪。最常見的就是齒輪齒條式和循環(huán)球式。 齒輪齒條式轉向器 齒輪齒條式轉向器迅速成為轎車，小型卡車以及多功能越野車轉向器中最普遍的型式。 它確實是一種比較簡單的機構。一套出輪齒條嚙合裝置被封裝在一根金屬管子里，齒條分別從管子末端深處。有根 干，叫做轉向拉桿，分別連在管架的末端。 齒輪齒條轉向器的齒輪是連在轉向軸上的。當轉動方向盤時，齒輪轉動推動齒條移動。齒條末端的橫拉桿連接于轉向節(jié)上的轉向臂上。 齒輪齒條轉系機構做完成兩件事： 它將方向盤的轉動轉化成轉動車輪所需要的直線運動。 在大多數汽車上，一般需要轉動三到四圈方向盤才能使車輪從左止點到右止點。 轉向系傳動比是指轉動方向盤角度和車輪轉動角度的比率。具體說就是，如果轉動方向盤一周車輪隨之轉動二十度，實際上轉向傳動比是 360 除以 20，也就是 18： 1。跟高的轉向傳動比意味著你需要更大的方向 盤轉角才能達到同樣的車輪轉角。當然，高傳動比也意味著更小的力量。 大體說來，質量小，更為運動型的汽車相比大型轎車和卡車擁有更小的轉向比。小傳動比意味著更快的轉向反應 -你無需再費力的轉動方向盤才能達到指定的車輪轉角 這就是跑車所要求的理想特性。這些小型汽車可以用更小的轉向比，因為在質量上足夠輕，轉動車輪所需的轉向力并沒超過要求。 一 部分 汽車 使用 可變轉向比，它使用一 種在中間和兩邊具有 不同的齒間距 的齒輪齒條嚙合裝置。 這使得汽車 在剛開始轉彎后能 迅速 做出 反應 （齒條在中間位置附近） ，同時也降低了 轉向力限制位置時的轉向 力 。 動力齒輪齒條轉向系統(tǒng) 當 齒輪齒條在動力轉向系統(tǒng)中時，齒條的設計略有不同 。 齒條中間位置包 含 有一個 氣缸與活塞?；钊B接到 齒條 上。 在活塞兩端各有一個液壓缸 。 在活塞的一端提供 高壓 油液以推動活塞移動，繼而推動齒條移動，提供轉向助力。 在接下來的段落里， 我們