汽车制动系统--英语

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汽车制动系统--英语The braking system is the most important system in cars. If the brakes fail， the result can be disastrous. Brakes are actually energy conversion devices， which convert the kinetic energy (momentum) of the vehicle into thermal energy (heat).When stepping on the brakes， the driver commands a stopping force ten times as powerful as the force that puts the car in motion. The braking system can exert thousands of pounds of pressure on each of the four brakes.
Two complete independent braking systems are used on the car. They are the service brake and the parking brake.
The service brake acts to slow， stop， or hold the vehicle during normal driving. They are foot-operated by the driver depressing and releasing the brake pedal. The primary purpose of the brake is to hold the vehicle stationary while it is unattended. The parking brake is mechanically operated by when a separate parking brake foot pedal or hand lever is set.
The brake system is composed of the following basic components: the master cylinder” which is located under the hood， and is directly connected to the brake pedal， converts driver foots mechanical pressure into hydraulic pressure. Steel brake lines” and flexible brake hoses” connect the master cylinder to the slave cylinders” located at each wheel. Brake fluid， specially designed to work in extreme conditions， fills the system. Shoes” and pads” are pushed by the slave cylinders to contact the drums” and rotors” thus causing drag， which (hopefully) slows the car.
The typical brake system consists of disk brakes in front and either disk or drum brakes in the rear connected by a system of tubes and hoses that link the brake at each wheel to the master cylinder (Figure).
Basically， all car brakes are friction brakes. When the driver applies the brake， the control device forces brake shoes， or pads， against the rotating brake drum or disks at wheel. Friction between the shoes or pads and the drums or disks then slows or stops the wheel so that the car is braked.
At the wheels， the fluid pushes shoes， or pads， against revolving drums or disks. The friction between the stationary shoes， or pads， and the revolving drums or disks slows and stops them. This slows or stops the revolving wheels， which， in turn， slow or stop the car.
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