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1、UNIT 10 BRAKING SYSTEMS TEXT A Basic Braking System and ABS,PROFESSIONAL ENGLISH,UNIT 8 Basic Braking System and ABS TEXT A Basic operating principle of the hydraulic system Disc brakes Drum brakes ABS Components Operating principle Types of Anti-Lock Brakes,本次课学习内容,本次课学习目标,掌握制动系统的有关英文专业词汇 掌握制动系统主要部
2、件工作原理 训练快速阅读能力，提高阅读速度,NEW WORDS,PHRASES AND EXPRESSIONS,Basic Braking System and ABS In order to reduce the speed of the vehicle，the brakes have to convert the kinetic energy stored in the vehicle to heat energy. A braking system consists of an energy-supplying device，a control device，a transmission
3、 device and the brake. Today，there are three types of braking systems in use: service braking system，parking braking system and additional retarder braking system. The service braking system and the parking braking system have separate control and transmission devices. The service braking system is
4、normally foot-operated，while the parking braking system is hand-operated. Basic operating principle of the hydraulic system Hydraulic systems are used to actuate the brakes of all small cars. The system transports the power required to force the frictional surfaces of the braking system together fro
5、m the pedal to the individual brake units at each wheel.,The master cylinder consists of a fluid reservoir and a double cylinder and piston assembly. Double type master cylinders are designed to separate the front and rear braking systems hydraulically in case of a leak. Steel lines carry the brake
6、fluid to a point on the vehicle frame near each of the vehicles wheels. The fluid is then carried to the calipers and wheel cylinders by flexible tubes in order to allow for suspension and steering movements. The hydraulic system operates as follows: When at rest，the entire system，from the piston(s)
7、 in the master cylinder to those in the wheel cylinders or calipers，is full of brake fluid. Upon application of the brake pedal，fluid trapped in front of the master cylinder piston(s) is forced through the lines to the wheel cylinders. Here，it forces the pistons outward，in the case of drum brakes，an
8、d inward toward the disc，in the case of disc brakes. The motion of the pistons is opposed by return springs mounted outside the cylinders in drum brakes，and by spring seals，in disc brakes.,Upon release of the brake pedal，a spring located inside the master cylinder immediately returns the master cyli
9、nder pistons to the normal position. The pistons contain check valves and the master cylinder has compensating ports drilled in it. These are uncovered as the pistons reach their normal position. The piston check valves allow fluid to flow toward the wheel cylinders or calipers as the pistons withdr
10、aw. Then，as the return springs force the brake pads or shoes into the released position，the excess fluid reservoirs through the compensating ports. It is during the time the pedal is in the released position that any fluid that has leaked out of the system will be replaced through the compensating p
11、orts 1. Dual circuit master cylinders employ two pistons，located one behind the other，in the cylinder. The primary piston is actuated directly by mechanical linkage from the brake pedal through the power booster. The secondary piston is actuated by fluid trapped between the two pistons.,If a leak de
12、velops in front of the secondary piston，it moves forward until it bottoms against the front of the master cylinder，and the fluid trapped between the pistons will operate the rear brakes. If the rear brakes develop a leak，the primary piston will move forward until direct contact with the secondary pi
13、ston takes place，and it will force the secondary piston to actuate the front brakes. In either case，the brake pedal moves farther when the brakes are applied，and less braking power is available. Disc brakes（自学） Instead of the traditional expanding brakes that press outward against a circular drum，di
14、sc brake systems utilize a disc (rotor) with brake pads positioned on either side of it. Braking effect is achieved in a manner similar to the way you would squeeze a spinning phonograph record between your fingers. The disc (rotor) is a casting with cooling fins between the two braking surfaces.,Th
15、is enables air to circulate between the braking surfaces making them less sensitive to heat buildup and more resistant to fade. Dirt and water do not affect braking action since contaminants are thrown off by the centrifugal action of the rotor or scraped off by the pads. Also，the equal clamping act
16、ion of the two brake pads tends to ensure uniform，straight line stops. Disc brakes are inherently self-adjusting. There are three general types of disc brake: fixed caliper，floating caliper and sliding caliper. The fixed caliper design uses two pistons mounted on either side of the rotor (in each side of the caliper). The caliper is mounted rigidly and does not move. The sliding and floating designs are quite similar. In fact，these two types are often lumped toget
