新编汽车专业英语第3版黄汽驰电子课件Unit5PassageA.pptxVIP

Unit Five Automobile Braking System　 Passage ATypes of BrakesAutomotive braking system isthe most important safety system on a car． It contains a group of mechanical, electronic and hydraulic components． Typically, each car has two completely independent brakes according to the different functions． One is service brake and the other is parking brake．Service brakeService brake is foot-operated by depressing the brake pedal to make a moving car slow down or stop during normal driving． It is also called foot brake which accomplishes through a hydraulic system．Parking brakeParking brake is used to keep an unattended car stationary and prevent the car from rolling down a hill． It is also called hand brake which is done by mechanical system such as a series of cables (see Fig.5-1).Typically, the braking system consists of disk brakes on the front wheels and drum brakes on the rear wheels (see Fig.5-2). Some cars may have disk brakes on all wheels, but the principle is the same in any case．Disk brakeDisk brake is comprised of a brake disk, brake pads and a brake caliper (see Fig.5-3).It works by causing two brake pads to press on either side of the brake disk that is rotating along with the wheel．Brake disk is sometimes called disk rotor mounted on the wheel hub． The disk has highly machined surfaces where the brake pads contact it． Between the two sides of the brake disk are vents that help it cool down (see Fig.5-4).Two brake pads are mounted in the brake caliper, one on each side of the brake disk． Each brake pad has a friction lining bonded on it． The friction linings are tough, very heat-resistant material (see Fig.5-5).Brake caliper contains one or more pistons which transmit the brake force hydraulically to the disk． The most common type of the brake caliper on modern cars is the single-piston floating caliper (see Fig.5-6). It is self-centering and self-adjusting． The brake caliper is able to slide from side to side so it will move to the center each time the brake