外文翻译---制动系统.docxVIP

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