汽車車輛工程畢業(yè)外文翻譯、制動器外文文獻翻譯、中英文翻譯

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. 譯文： 制動器 制動器：它們的作用？ 簡單的說：它會使你的汽車慢下來。 復(fù)雜的說：制動器被用來讓你的車減速，但可能不是你所想的意思。普遍的誤解是，制動器擠壓制動鼓或制動片，擠壓的壓力的作用使你的車慢下來。但這只是制動的一部分。制動系統(tǒng)本質(zhì)上是改變能量的類型。當(dāng)你在全速行駛時，你的汽車獲得動能。當(dāng)你踩下剎車，墊子或鞋子對制動鼓和轉(zhuǎn)子的作用轉(zhuǎn)化為摩擦熱能。剎車的冷卻使車的熱能消散，減慢車速。這是熱力學(xué)第一定律，有時被視為能量守恒定律。 也是就說：能量不能被創(chuàng)造也不能被消滅，只能由一種形式轉(zhuǎn)換成另一種。 制動 情況下，它是動能轉(zhuǎn)化為熱能。 角向力。 因為在盤式制動器的剎車片和轉(zhuǎn)子的位置，摩擦產(chǎn)生的 接觸 點的位置也產(chǎn)生了一個機械的抵御轉(zhuǎn)子的回轉(zhuǎn)運動。 熱力學(xué)，制動失效，鉆孔轉(zhuǎn)子。 如果你騎摩托車或駕駛一輛賽車，你或許熟悉制動失效，描述 當(dāng)制動器太熱，他發(fā)生了什么 。一個很好的例子就是從山上下來使用剎車制動 ,而不是你的引擎使你減速。當(dāng)汽車開始滑動下來時，剎車使汽車產(chǎn)生熱能 ,使你減速 。但是如果你持續(xù)使用他們， 轉(zhuǎn)子或鼓留 熱 并沒有機會冷卻 。從某種意義上說他們不能吸收更多的熱量， 使剎車墊熱了起來 。在每一個墊子的摩擦材料有某種共同的樹脂一旦開始變得太熱，該樹脂開始蒸發(fā)，形成氣。由于氣體之間不能待在墊層及轉(zhuǎn)子，而是形成薄薄的一層在兩個之間準備排走。 墊失去與轉(zhuǎn)子的接觸， 減少摩擦和熱量。這是完全的制動失效。 典型的補救辦法，將車停了下來，等待幾分鐘。 由于制動部件降溫，吸收熱量的原因，下一次您使用剎車的能力，似乎會好一點。這種類型的制動失效在舊車輛更常見。 新的車輛 往往從剎車墊中減少排氣， 但他們?nèi)杂兄?動失效。為什么呢？ 它仍然因為剎車墊太熱。 猶由于新的剎車墊合成，襯墊的熱傳遞到卡鉗一旦轉(zhuǎn)子太熱了，制動液開始 沸騰冒泡 。因為空氣是可壓縮的(制動液不是 )當(dāng)你踩剎車，氣泡的壓縮代替了流體轉(zhuǎn)移到制動卡鉗。這就是現(xiàn)代制動失效。 工程師們是怎樣設(shè)計減少或消除剎車制動失效的 ? 年長的車輛，是使氣化的氣體有地方排掉。新的車輛，找到一些方式來冷卻轉(zhuǎn)子更為有效。無論如何你最終獲得 交叉鉆孔 或溝槽剎車盤。當(dāng)槽表面是可以減少比熱容量的轉(zhuǎn)子，其效果可以忽略不計的。然而當(dāng)大力剎車時一旦一切都是熱和樹脂材料蒸發(fā)，槽讓氣體排去， 所以墊可以 繼續(xù)接觸轉(zhuǎn)子，讓車減速停下來。 整個的理解能量轉(zhuǎn)換的關(guān)鍵是，剎車他們該做什么 ,以及為什么它們設(shè)計成這樣。如果你曾看過一級方程式賽車，你就可以看到向前的前輪里面有很大的洞（如上圖所示）。 這是管道空氣剎車部件，以幫助他們冷卻下來， 因為在 F1 賽車中，剎車每隔幾秒鐘頻繁使用，花很多時間預(yù)留熱量。如果沒有某種冷卻協(xié)助，剎車就可能在最開始的幾個轉(zhuǎn)角失靈，最后剎車失效賽車在一半路程出局。 轉(zhuǎn)子技術(shù)。 如果制動轉(zhuǎn)子是一個單一的鋼鐵鑄塊，這將有嚴重的散熱性能和氣化氣無法排去 。因此， 剎車盤通常使用各種額外的設(shè)計特點的方式來改進 幫助他們冷卻下來，盡快使墊和轉(zhuǎn)子之間的任何氣體排走。 這里的圖表顯示了轉(zhuǎn)子類型的各種修改，可以改進幫助他們創(chuàng)造更多的摩擦力，更 迅速地驅(qū)散更多的熱量，通風(fēng)氣體的一些例子。 從左至右。 1：基本制動轉(zhuǎn)子。 2：溝槽轉(zhuǎn)子 -溝槽給予更多口，他們之間產(chǎn)生更多的摩擦，還 允許氣體從墊和轉(zhuǎn)子之間的排走 。 3：溝槽鉆孔轉(zhuǎn)子 -再給多一點口，但也讓氣流 (渦旋 )通過制動盤協(xié)助冷卻和通風(fēng)。 4：雙通風(fēng)轉(zhuǎn)子-以前一樣，然而現(xiàn)在有了兩個轉(zhuǎn)子而不是一個，和他們之間葉片產(chǎn)生渦流將進一步冷卻轉(zhuǎn)子同時試圖實際上從襯墊中排掉任何氣體。 重要的一點：鉆孔轉(zhuǎn)子通常只使用于賽車。鉆孔使得轉(zhuǎn)子變?nèi)?，通常會?dǎo)致轉(zhuǎn)子產(chǎn)生各類裂縫。在賽車中這不是一個問 題 在每場比賽或者每周都會更換剎車盤。但在路上的車，最終會導(dǎo)致剎車轉(zhuǎn)子失靈的，不是你能想象的。我只提這件事，因為有許多供應(yīng)商將為您提供鉆孔轉(zhuǎn)子，沒有直接提到這個事實。 大轉(zhuǎn)子。 這是如何適用于更大的剎車轉(zhuǎn)子 -一種普遍的跑車升級？汽車和自行車運動比賽通常有比一般的家庭汽車更大的盤或轉(zhuǎn)子。一個更大的轉(zhuǎn)子有更多的材料在里面，因此它可以吸收更多的熱量。更多