机电技术专业英语课件作者徐起贺张庆良patablessonFive.pptVIP

尚辅网 / 机电技术专业英语 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 form 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 possible 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 friction 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 wheel 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 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 pushed the piston of the brake master cylinder which presses the fluid. The fluid flows through the pipelines to the power brake unit and then