外文翻译---制动系统.docx

附 录1Hydraulic Brake SystemsThe braking system is the most important system in cars. If the brake system fail, the result can be disastrous.When you step on the brake pedal, you expect the vehicle to stop. The brake pedal operates a hydraulic system that is used for two reasons. First, fluid under pressure can be carried to all parts of the vehicle by small hoses or metal lines with out taking up a lot of room or causing routing problems. Second, the hydraulic fluid offers a great mechanical advantage-little foot pressure is required on the pedal, but a great deal of pressure is generated at the wheels. The brake pedal is linked to a piston in the brake master cylinder, which is filled with hydraulic brake fluid. The master cylinder consists of a cylinder containing a small piston and a fluid reservoir.Modern master cylinders are actually two separate cylinders. Such a system is called a dual circuit, because the front cylinder is connected to the front brakes and the rear cylinder to the rear brakes. (Some vehicles are connected diagonally.) The two cylinders are actually separated, allowing for emergency stopping power should one part of the system fail.The entire hydraulic system from the master cylinder to the wheels is full of hydraulic brake fluid. When the brake pedal is depressed, the pistons in the master cylinder are forced to move, exerting tremendous force on the fluid in the lines. The fluid has nowhere to go, and forces the wheel cylinder pistons (drum brakes) or caliper pistons (disc brakes) to exert pressure on the brake shoes or pads. The friction between the brake shoe and wheel drum or the brake pad and rotor (disc) slows the vehicle and eventually stops it.Also attached to the brake pedal is a switch that lights the brake lights as the pedal is depressed. The lights stay on until the brake pedal is released and returns to its normal position.Each wheel cylinder in a drum brake system contains two pistons, one at either end, which push outward in opposite directions. In disc brake systems, the wheel cylinders are part of the caliper (there can be as many as four or as few as one). Whether disc or drum type, all pistons use some type of rubber seal to prevent leakage around the piston, and a rubber dust boot seals the outer ends of the wheel cylinders against dirt and moisture.When the brake pedal is released, a spring pushes the master cylinder pistons back to their normal positions. Check valves in the master cylinder piston allow fluid to flow toward the wheel cylinders or calipers as the piston returns. Then as the brake shoe return springs pull the brake shoes back to the released position, excess fluid returns to the master cylinder through compensating ports, which have been uncovered as the pistons move back. Any fluid that has leaked from the system will also be replaced through the compensating ports.All dual circuit brake systems use a switch to activate a light, warning of brake failure. The switch is located in a valve mounted near the master cylinder. A piston in the valve receives pressure on each end from the front and rear brake circuits. When the pressures are balanced, the piston remains stationary, but when one circuit has a leak, greater pressure during the application of the brakes will force the piston to one side or the other, closing the switch and activating the warning light. The light can also be activated by the ignition switch during engine starting or by the parking brake.Front disc, rear drum brake systems also have a metering valve to prevent the front disc brakes from engaging before the rear brakes have contacted the drums. This ensures that the front brakes will not normally be used alone to stop the vehicle. A proportioning valve is also used to limit pressure to the rear brakes to prevent rear wheel lock-up during hard braking.1. Friction materialsBrake shoes and pads are constructed in a similar manner. The pad or shoe is composed of a metal backing plate and a friction lining. The lining is either bonded (glued) to the metal, or riveted. Generally, riveted linings provide superior performance, but good quality bonded linings are perfectly adequate.Friction materials will vary between manufacturers and type of pad and the material compound may be referred to as: asbestos, organic, semi-metallic, metallic. The difference between these compounds lies in the types and percentages of friction materials used, material binders and performance modifiers.Generally speaking, organic and non-metallic asbestos compound brakes are quiet, easy on rotors and provide good feel. But this comes at the expense of high temperature operation, so they may not be your best choice for heavy duty use or mountain driving. In most cases, these linings will wear somewhat faster than metallic compound pads, so you will usually replace them more often. But, when using these pads, rotors tend to last longer.Semi-metallic or metallic compound brake linings will vary in performance based on the metallic contents of the compound. Again, generally speaking, the higher the metallic content, the better the friction material will resist heat. This makes them more appropriate for heavy duty applications, but at the expense of braking performance before the pad reaches operating temperature. The first few applications on a cold morning may not give strong braking. Also, metallic and semi-metallic are more likely to squeal. In most cases, metallic compounds last longer than non-metallic pads, but they tend to cause more wear on the rotors. If you use metallic pads, expect to replace the rotors more often.When deciding what type of brake lining is right for you, keep in mind that todays modern cars have brake materials which are matched to the expected vehicles performance capabilities. Changing the material from OEM specification could adversely affect brake feel or responsiveness. Before changing the brake materials, talk to your dealer or parts supplier to help decide what is most appropriate for your application. Remember that heavy use applications such as towing, stop and go driving, driving down mountain roads, and racing may require a change to a higher performance material.Some more exotic materials are also used in brake linings, among which are Kevlar and carbon compounds. These materials have the capability of extremely good performance for towing, mountain driving or racing. Wear characteristics can be similar to either the metallic or the non-metallic linings, depending on the product you buy. Most race applications tend to wear like metallic linings, while many of the street applications are more like the non-metallic. 2. Brake fluidOn a disk brake, the fluid from the master cylinder is forced into a caliper where it presses against a piston. The piston, in-turn, squeezes two brake pads against the disk(rotor)which is attached to the wheel, forcing it to slow down or stop. This process is similar to a bicycle brake where two rubber pads rub against the wheel rim creating friction.With drum brakes, fluid is forced into the wheel cylinder which pushes the brake shoes out so that the friction linings are pressed against the drum which is attached to the wheel, causing the wheel to stop.In either case, the friction surfaces of the pads on a disk brake system, or the shoes on a drum brake convert the forward motion of the vehicle into heat. Heat is what causes the friction surfaces (linings) of the pads and shoes to eventually wear out and require replacement.Brake fluid is a special oil that has specific properties. It is designed to withstand cold temperatures without thickening as well as very high temperatures without boiling.(If the brake fluid should boil, it will cause you to have a spongy pedal and the car will be hard to stop). Figure shows a brake hydraulic system.The brake fluid reservoir is on top of the master cylinder. Most cars today have a transparent r reservoir so that you can see the level without opening the cover. The brake fluid level will drop slightly as the brake pads wear. This is a normal condition and no cause for concern. If the level drops noticeably over a short period of time or goes down to about two thirds full, have your brakes checked as soon as possible. Keep the reservoir covered except for the amount of time you need to fill it and never leave a cam of brake fluid uncovered. Brake fluid must maintain a very high boiling point. Exposure to air will cause the fluid to absorb moisture which will lower that boiling point.The brake fluid travels from the master cylinder to the wheels through a series of steel tubes and reinforced rubber hoses. Rubber hoses are only used in places that require flexibility, such as at the front wheels, which move up and down as well as steer. The rest of the system uses non-corrosive seamless steel tubing with special fittings at all attachment points. If a steel line requires a repair, the best procedure is to replace the compete line. If this is not practical, a line can be repaired using special splice fittings that are made for brake system repair. You must never use copper tubing to repair a brake system. They are dangerous and illegal. 制动系统制动系统是汽车中最重要的系统。 如果制动系统失效，结果可能是损失惨重的。当你踩在制动器的踏板上，你希望把车辆停下来。制动器的踏板操纵着制动系统，其原因有二。首先，具有一定压力的制动液通过制动管路被输送到制动系统的制动主缸中，这不需占据很多空间或导致线路问题。其次，制动液提供踏板所需要的强机械压力，但是大部分压力作用在车轮上。制动踏板和制动主缸里的主缸活塞相连，主缸里充满了液压制动液。主缸由一个活塞和一个贮液罐组成。现代主缸实际上有两个分离的气缸。这样的系统叫做双环行。因为前面的汽缸和前闸相连，后部的气缸和后闸相连（有些车辆采用对角线相连接的方法）这两个气缸是分离的，在紧急刹车情况下，这个系统的一部分将失去作用。整个液压系统从主缸到车轮充满着液压制动流体。当踩下制动器踏板，主缸上的活塞便跟着运转，这就向管路中的液体施加了很大的压力。制动液被迫作用于气缸活塞（鼓式制动器）或卡钳活塞（盘式制动闸）从而施加压力于制动蹄片和衬垫。制动蹄片和车轮之间或制动衬垫和制动盘之间的摩擦使车辆减速，最终使它停下来。依附于制动器踏板上的是一个开关，当踩下踏板时，制动器的灯也随之点亮。直到松开制动器踏板并且踏板回到原位置时，灯才熄灭。在每一个鼓式制动系统的制动轮缸里，都有两个活塞。其中一个在一边的终端，这个活塞向外面的相反方向推动。在盘式制动系统中，制动轮缸是制动钳的一部分（制动轮缸多则四个，少则两个）无论盘式制动器还是鼓式制动器，所有活塞均采用某种类型的橡胶封口以防活塞周围的泄漏。制动轮缸的外终端加之橡胶防尘封口，用以防止脏物和潮湿。当松开制动器踏板，主缸的回味弹簧推动主缸活塞回到正常位置。主缸活塞里的单向闸使液体流向制动轮缸或制动钳，活塞向回运动。然后，随着制动蹄片的返回，回位弹簧推动制动蹄片回到释放状态下的原始位置，通过补偿气孔，流体返回到主缸，补偿孔一直打开，直至活塞返回到原始位置。系统中泄漏的流体将通过补偿孔中的流体得到代替。双环形制动系统使用一个开关来点灯，以警示制动器失效。这个开关在主缸附近的一个闸门里。闸门里的活塞受力，作用一边前后的制动环路。当压力平衡时，活塞保持静止，但是当一个环路中出现泄漏时，制动器作用过程中的强大压力迫使活塞从一边到另一边，同时开关关闭，警示灯亮起。在发动机启动或制动器停止的过程中，通过点火装置的开火也可使灯点亮。前轮用盘式，后面用鼓式制动系统也有一个计量器阀门防止前面的盘闸门和后面的闸门连接到鼓形装置之前运作。这也确保了前闸不会单独用于停止车辆。一个比例恰当的闸门通常用来为后面的制动系统减压，以防止在艰难的刹车状态下后面的轮子不听使唤。1 摩擦材料制动蹄片和衬垫以相似的方式构成。衬垫或蹄片用金属板材和摩擦衬料组成。衬料联结（粘贴）或铆接在金属上。一般来说，铆接衬料更具优越性，但是高质量的联结（粘贴）材料同样合适。摩擦材料因规格，衬垫的类型，材料的复合情况而不同，通常分为：石棉，有机材料，非金属，金属。这些复合物的差异在于它们的类型，摩擦材料所用的百分比，材料黏合剂和调节剂的使用。一般来说，有机材料和非金属石棉复合制动器声音较低，但这种制动器