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1、,机电技术专业英语,2,Lesson Five,Text,The most vital factor in the running and control of the modern vehicles is the braking system. In order to bring the moving motor vehicle to rest or slow down in the shortest possible time, the energy of motion possessed by the vehicle must be converted into some other f
2、orm of energy. The rate of slowing down or retardation is governed by the speed of conversion of energy. Kinetic energy is the energy of motion which is converted into heat given up to air flowing over the braking system. The means of slowing down or bring to rest a moving vehicle in the shortest po
3、ssible distance is called brakes.,Brakes,Lesson Five,Brake is a friction device for converting the power or momentum or kinetic energy of the moving vehicle into heat by means of friction. It is the main factor governing even if sufficient effort is available to lock the wheels. This amount of frict
4、ion developed between two surfaces in contact is independent of the area of the surface in contact. The brake system comprises the brake assemblies and means to apply the brakes. The modern automobiles use two types of brake assemblies: wheel brakes and drive shaft brakes. There are two types of whe
5、el brakes, the drum brake and the disc brake. The wheel brake, as the name implies, is located in the wheel. Figure B.3 is shown a drum brake assembly controlled hydraulically. It consists of the brake drum, an expander, pull back springs, a stationary backplate, two shoes with friction linings, and
6、 anchor pins. The stationary back plate is secured to the flange of the axle housing or to the steering knuckle. The brake drum is mounted on the wheel hub. There is a clearance between the inner surface of the drum and the shoe lining.,Lesson Five,When the drum brake pedal is depressed, the rod pus
7、hed the piston of the brake master cylinder which presses the fluid. The fluid flows through the pipelines to the power brake unit and then to the wheel cylinders. The fluid pressure expands the cylinder pistons thus pressing the shoes to the drum. If the pedal is released, the piston returns to the
8、 initial position, the pull back springs retract the shoes, the fluid is forced back to the master cylinder and braking ceases (Figure B.3).,Lesson Five,Figure B.3 Operation of braking system 1.braking pedal; 2.push rod; 3.master cylinder piston; 4.master cylinder; 5.hydraulic lines; 6.wheel cylinde
9、r; 7.wheel cylinder pistons; 8.brake drum; 9.friction linings; 10.brake shoes; 11.back plate; 12.anchor pins; 13.pull back springs,Lesson Five,New Words and Expressions,Lesson Five,Lesson Five,Notes,The car may now be left without fear of its rolling away. 离开汽车时不用担心它会滑跑。 of用作介词，表示原因。,谢谢观赏,,Thank You !,
