汽车车辆工程毕业外文翻译、制动器外文文献翻译、中英文翻译

外文原文： THE BRAKE BIBLE Brakes - what do they do? The simple answer: they slow you down. The complex answer: brakes are designed to slow down your vehicle but probably not by the means that you think. The common misconception is that brakes squeeze against a drum or disc, and the pressure of the squeezing action is what slows you down. This in fact is only part of the equation. Brakes are essentially a mechanism to change energy types. When youre travelling at speed, your vehicle has kinetic energy. When you apply the brakes, the pads or shoes that press against the brake drum or rotor convert that energy into thermal energy via friction. The cooling of the brakes dissipates the heat and the vehicle slows down. It s the F irst Law of Thermodynamics, sometimes known as the law of conservation of energy. This states that energy cannot be created nor destroyed, it can only be converted from one form to another. In the case of brakes, it is converted from kinetic energy to thermal energy. Angular force . Because of the configuration of the brake pads and rotor in a disc brake, the location of the point of contact where the friction is generated also provides a mechanical moment to resist the turning motion of the rotor. Thermodynamics, brake fade and drilled rotors. If you ride a motorbike or drive a race car, youre probably familiar with the term brake fade, used to describe what happens to brakes when they get too hot. A good example is coming down a mountain pass using your brakes rather than your engine to slow you down. As you start to come down the pass, the brakes on your vehicle heat up, slowing you down. But if you keep using them, the rotors or drums stay hot and get no chance to cool off. At some point they can t absorb any more heat so the brake pads heat up instead. In every brake pad there is the friction material that is held together with some sort of resin and once this starts to get too hot, the resin starts to vapourise, forming a gas. Because the gas cant stay between the pad and the rotor, it forms a thin layer between the two whilst trying to escape. The pads lose contact with the rotor, reducing the amount of friction and voila. Complete brake fade. The typical remedy for this would be to get the vehicle to a stop and wait for a few minutes. As the brake components cool down, their ability to absorb heat returns and the next time you use the brakes, they seem to work just fine. This type of brake fade was more common in older vehicles. Newer vehicles tend to have less outgassing from the brake pad compounds but they still suffer brake fade. So why? Its still to do with the pads getting too hot. With newer brake pad compounds, the pads transfer heat into the calipers once the rotors are too hot, and the brake fluid starts to boil forming bubbles in it. Because air is compressible (brake fluid isnt) when you step on the brakes, the air bubbles compress instead of the fluid transferring the motion to the brake calipers. Voila. Modern brake fade. So how do the engineers design brakes to reduce or eliminate brake fade? For older vehicles, you give that vapourised gas somewhere to go. For newer vehicles, you find some way to cool the rotors off more effectively. Either way you end up with cross-drilled or grooved brake rotors. While grooving the surface may reduce the specific heat capacity of the rotor, its effect is negligible in the grand scheme of things. However, under heavy braking once everything is hot and the resin is vapourising, the grooves give the gas somewhere to go, so the pad can continue to contact the rotor, allowing you to stop. The whole understanding of the conversion of energy is critical in understanding how and why brakes do what they do, and why they are designed the way they are. If you ve ever watched Formula 1 racing, you ll see the front wheels have huge scoops inside the wheel pointing to the front (see the picture above). This is to duct air to the brake components to help them cool off because in F1 racing, the brakes are used viciously every few seconds and spend a lot of their time trying to stay hot. Without some form of cooling assistance, the brakes wo uld be fine for the first few corners but then would fade and become near useless by half way around the track. Rotor technology. If a brake rotor was a single cast chunk of steel, it would have terrible heat dissipation properties and leave nowhere for t he vapourised gas to go. Because of this, brake rotors are typically modified with all manner of extra design features to help them cool down as quickly as possible as well as dissapate any gas from between the pads and rotors. The diagram here shows some examples of rotor types with the various modification that can be done to them to help them create more friction, disperse more heat more quickly, and ventilate gas. From left to right. 1: Basic brake rotor. 2: Grooved rotor - the grooves give more bite and thus more friction as they pass between the brake pads They also allow gas to vent from between the pads and the rotor. 3: Grooved, drilled rotor - the drilled holes again give more bite, but also allow air currents (eddies) to blow through the brake disc to assist cooling and ventilating gas. 4: Dual ventilated rotors - same as before but now with two rotors instead of one, and with vanes in between them to generate a vortex which will cool the rotors even further whilst trying to actually suck any gas away from the pads. An important note about drilled rotors: Drilled rotors are typically only found (and to be used on) race cars. The drilling weakens the rotors and typically results in microfractures to the rotor. O n race cars this isnt a problem - the brakes are changed after each race or weekend. But on a road car, this can eventually lead to brake rotor failure - not what you want. I only mention this because of a lot of performance suppliers will supply you with drilled rotors for street cars without mentioning this little fact. Big rotors. How does all this apply to bigger brake rotors - a common sports car upgrade? Sports cars and race bikes typically have much bigger discs or rotors than your average family car. A bigger rotor has more material in it so it can absorb more heat. More material also means a larger surface area for the pads to generate friction with, and better heat dissipation. Larger rotors also put the point of contact with the pads further away from the ax le of rotation. This provides a larger mechanical advantage to resist the turning of the rotor itself. To best illustrate how this works, imagine a spinning steel disc on an axle in front of you. If you clamped your thumbs either side of the disc close to the middle, your thumbs would heat up very quickly and youd need to push pretty hard to generate the friction required to slow the disc down. Now imagine doing the same thing but clamping your thumbs together close to the outer rim of the disc. The disc w ill stop spinning much more quickly and your thumbs wont get as hot. That, in a nutshell explains the whole principle behind why bigger rotors = better stopping power. The different types of brake. All brakes work by friction. Friction causes heat which is part of the kinetic energy conversion process. How they create friction is down to the various designs. Bicycle wheel brakes I thought Id cover these because they re about the most basic type of functioning brake that you can see, watch working, and understand. The construction is very simple and out-in-the-open. A pair of rubber blocks are attached to a pair of calipers which are pivoted on the frame. When you pull the brake cable, the pads are pressed against the side or inner edge of the bicycle wheel rim. The rubber creates friction, which creates heat, which is the transfer of kinetic energy that slows you down. Theres only really two types of bicycle brake - those on which each brake shoe shares the same pivot point, and tho se with two pivot points. If you can look at a bicycle brake and not understand whats going on, the rest of this page is going to cause you a bit of a headache. Drum brakes - single leading edge The next, more complicated type of brake is a drum brake. The concept here is simple. Two semicircular brake shoes sit inside a spinning drum which is attached to the wheel. When you apply the brakes, the shoes are expanded outwards to press against the inside of the drum. This creates friction, which creates he at, which transfers kinetic energy, which slows you down. The example below shows a simple model. The actuator in this case is the blue elliptical object. As that is twisted, it forces against the brake shoes and in turn forces them to expand outwards. The return spring is what pulls the shoes back away from the surface of the brake drum when the brakes are released. See the later section for more information on actuator types. The single leading edge refers to the number of parts of the brake shoe which actually contact the spinning drum. Because the brake shoe pivots at one end, simple geometry means that the entire brake pad cannot contact the brake drum. The leading edge is the term given to the part of the brake pad which does contact the drum, and in the case of a single leading edge system, its the part of the pad closest to the actuator. This diagram (right) shows what happens as the brakes are applied. The shoes are pressed outwards and the part of the brake pad which first contacts the drum is the leading edge. The action of the drum spinning actually helps to draw the brake pad outwards because of friction, which causes the brakes to bite. The trailing edge of the brake shoe makes virtually no contact with the drum at all. This simple geometry explains why its really difficult to stop a vehicle rolling backwards if it s equipped only with single leading edge drum brakes. As the drum spins backwards, the leading edge of the shoe becomes the trailing edge and thus doesnt bite. Drum brakes - double leading edge The drawbacks of the single leading edge style of drum brake can be eliminated by adding a second return spring and turning the pivot point into a second actuator. Now when the brakes are applied, the shoes are pressed outwards at two points. So each brake pad now has one leading and one trailing edge. Because there are two brake shoes, there are two brake pads, which means there are two leading edges. Hence the name double leading edge. Disc brakes Some background. Disc brakes were invented in 1902 and patented by Birmingham car maker Frederick William Lanchester. His original design had two discs which pressed against each other to generate frict ion and slow his car down. It wasnt until 1949 that disc brakes appeared on a production car though. The obscure American car builder Crosley made a vehicle called the Hotshot which used the more familiar brake rotor and calipers that we all know and love today. His original design was a bit crap though - the brakes lasted less than a year each. F inally in 1954 Citron launched the way-ahead-of- its-time DS which had the first modern incarnation of disc brakes along with other nifty stuff like self- levelling suspension, semi- automatic gearbox, active headlights and composite body panels. (all things which were re-introduced as new by car makers in the 90s). Disc brakes are an order of magnitude better at stopping vehicles than drum brakes, which is why you ll find disc brakes on the front of almost every car and motorbike built today. Sportier vehicles with higher speeds need better brakes to slow them down, so youll likely see disc brakes on the rear of those too. 译文： 制动器 制动器：它们的作用？ 简单的说：它会使你的汽车慢下来。 复杂的说：制动器被用来让你的车减速，但可能不是你所想的意思。普遍的误解是，制动器挤压制动鼓或制动片，挤压的压力的作用使你的车慢下来。但这只是制动的一部分。制动系统本质上是改变能量的类型。当你在全速行驶时，你的汽车获得动能。当你踩下刹车，垫子或鞋子对制动鼓和转子的作用转化为摩擦热能。刹车的冷却使车的热能消散，减慢车速。这是热力学第一定律，有时被视为能量守恒定律。 也是就说：能量不能被创造也不能被消灭，只能由一种形式转换成另一种。 制动 情况下，它是动能转化为热能。 角向力。 因为在盘式制动器的刹车片和转子的位置，摩擦产生的 接触 点的位置也产生了一个机械的抵御转子的回转运动。 热力学，制动失效，钻孔转子。 如果你骑摩托车或驾驶一辆赛车，你或许熟悉制动失效，描述 当制动器太热，他发生了什么 。一个很好的例子就是从山上下来使用刹车制动 ,而不是你的引擎使你减速。当汽车开始滑动下来时，刹车使汽车产生热能 ,使你减速 。但是如果你持续使用他们， 转子或鼓留 热 并没有机会冷却 。从某种意义上说他们不能吸收更多的热量， 使刹车垫热了起来 。在每一个垫子的摩擦材料有某种共同的树脂一旦开始变得太热，该树脂开始蒸发，形成气。由于气体之间不能待在垫层及转子，而是形成薄薄的一层在两个之间准备排走。 垫失去与转子的接触， 减少摩擦和热量。这是完全的制动失效。 典型的补救办法，将车停了下来，等待几分钟。 由于制动部件降温，吸收热量的原因，下一次您使用刹车的能力，似乎会好一点。这种类型的制动失效在旧车辆更常见。 新的车辆 往往从刹车垫中减少排气， 但他们仍有制 动失效。为什么呢？ 它仍然因为刹车垫太热。 犹由于新的刹车垫合成，衬垫的热传递到卡钳一旦转子太热了，制动液开始 沸腾冒泡 。因为空气是可压缩的(制动液不是 )当你踩刹车，气泡的压缩代替了流体转移到制动卡钳。这就是现代制动失效。 工程师们是怎样设计减少或消除刹车制动失效的 ? 年长的车辆，是使气化的气体有地方排掉。新的车辆，找到一些方式来冷却转子更为有效。无论如何你最终获得 交叉钻孔 或沟槽刹车盘。当槽表面是可以减少比热容量的转子，其效果可以忽略不计的。然而当大力刹车时一旦一切都是热和树脂材料蒸发，槽让气体排去， 所以垫可以 继续接触转子，让车减速停下来。 整个的理解能量转换的关键是，刹车他们该做什么 ,以及为什么它们设计成这样。如果你曾看过一级方程式赛车，你就可以看到向前的前轮里面有很大的洞（如上图所示）。 这是管道空气刹车部件，以帮助他们冷却下来， 因为在 F1 赛车中，刹车每隔几秒钟频繁使用，花很多时间预留热量。如果没有某种冷却协助，刹车就可能在最开始的几个转角失灵，最后刹车失效赛车在一半路程出局。 转子技术。 如果制动转子是一个单一的钢铁铸块，这将有严重的散热性能和气化气无法排去 。因此， 刹车盘通常使用各种额外的设计特点的方式来改进 帮助他们冷却下来，尽快使垫和转子之间的任何气体排走。 这里的图表显示了转子类型的各种修改，可以改进帮助他们创造更多的摩擦力，更 迅速地驱散更多的热量，通风气体的一些例子。 从左至右。 1：基本制动转子。 2：沟槽转子 -沟槽给予更多口，他们之间产生更多的摩擦，还 允许气体从垫和转子之间的排走 。 3：沟槽钻孔转子 -再给多一点口，但也让气流 (涡旋 )通过制动盘协助冷却和通风。 4：双通风转子-以前一样，然而现在有了两个转子而不是一个，和他们之间叶片产生涡流将进一步冷却转子同时试图实际上从衬垫中排掉任何气体。 重要的一点：钻孔转子通常只使用于赛车。钻孔使得转子变弱，通常会导致转子产生各类裂缝。在赛车中这不是一个问 题 在每场比赛或者每周都会更换刹车盘。但在路上的车，最终会导致刹车转子失灵的，不是你能想象的。我只提这件事，因为有许多供应商将为您提供钻孔转子，没有直接提到这个事实。 大转子。 这是如何适用于更大的刹车转子 -一种普遍的跑车升级？汽车和自行车运动比赛通常有比一般的家庭汽车更大的盘或转子。一个更大的转子有更多的材料在里面，因此它可以吸收更多的热量。更多