1、Unit Five Automobile Braking System Passage ATypes of Brakes Automotive 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 i
2、s service brake and the other is parking brake Service brake Service 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 brake Parking brake is used to kee
3、p 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)
4、.Some cars may have disk brakes on all wheels,but the principle is the same in any case Disk brake Disk 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 Br
5、ake 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 d
6、isk 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-pi
7、ston 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 brakes are applied Also,it is cheaper and more reliable Drum brake Drum brake is comprised of two brake shoes,a wheel cylinder,a
8、n adjuster,an emergency brake mechanism,a back plate,a lot of return springs,and a brake drum as shown in Fig.5-7 Brake shoes are curved pieces of metal with the friction linings riveted on them that are moved hydraulically against the brake drum to stop its rotation Wheel cylinder with a piston is
9、a powerful mechanism,which exerthy draulic force on-to the brake shoes so they can contact the drum and stop the moving car with friction Adjuster is used to adjust the distance between the surface of the friction linings and the inside of brake drum Emergency brake mechanism is used in an emergency
10、,also used as a parking brake to prevent a car from rolling It is mechanical operated by a cable system,rather than a hydraulic one Back plate serves as the base for the brake shoes,the wheel cylinder,the adjuster and emergency brake mechanism They are all mounted on the back plate Brake drum is a h
11、ollow round steel drum that rotates along with the wheel The other drum brake components are located in the brake drumNew Words and Expressions independent indipendnt adj 独立的 unattended ntendid adj 无人看管的 stationary steinri adj 静止的 hub hb n 轮毂 vent vent n 通风孔 bonded bndid adj 粘接的 heat-resistant hi:tr
12、izistnt adj 抗热的,耐热的 self-centeringadj 自动定心的 self-adjusting selfdsti adj自动调节的,自调整 adjuster dst n 调节器 riveted rivitid adj 铆接的 in any case总之 be comprised of由组成Common Automobile Terms service brake行车制动器 parking brake驻车制动器 foot brake脚踏制动器,脚刹 hand brake驻车制动器,手刹 disk brake盘式制动器 drum brake鼓式制动器 brake pad制动衬块 friction lining摩擦片,摩擦衬片 brake caliper制动钳 brake fluid制动液 floating caliper浮动制动钳,浮钳Common Automobile Terms brake shoe制动蹄 wheel cylinder制动轮缸,制动分泵 back plate制动底板 return spring回位弹簧 brake drum制动鼓 emergency brake紧急制动器
