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1、5月12日14时28分，我国四川发生里氏8级地震 在地震发生的这一周内，3.4万同胞遇难，22万余人受伤 国务院已决定： 5月19日21日为全国哀悼日 5月19日14时28分，全国人民为地震灾区遇难同胞默哀3分钟 2008年5月19日12时,沉痛悼念汶川大地震遇难同胞,UNIT 9 AUTOMATIC TRANSMISSIONS TEXT A Automatic Transmission (AT),PROFESSIONAL ENGLISH,UNIT 8 AUTOMATIC TRANSMISSIONS TEXT A Automatic Transmission (AT) Torque Conve
2、rter Planetary Gear Hydraulic System Servos and Accumulators Hydraulic Control System Electronic Control System,本次课学习内容,本次课学习目标,掌握自动变速器的有关英文专业词汇 能够较好地用已知翻译技巧进行课文翻译 训练快速阅读能力，较高的阅读速度,NEW WORDS,PHRASES AND EXPRESSIONS,Automatic Transmission (AT) In todays automobile, the automatic transmission is by fa
3、r the most complicated mechanical component. It is a type of transmission that shifts itself. Automatic transmission or transaxle has four basic systems-a torque converter, a gear system, a hydraulic system and an electronic system (Fig. 9-1). TORQUE CONVERTER The torque converter replaces the conve
4、ntional clutch. It has three functions: 1. It allows the engine to idle with the vehicle at a standstill, even with the transmission or transaxle in gear1. 2. It allows the transmission or transaxle to shift from range-to-range smoothly, without requiring that the driver close the throttle during th
5、e shift. 3. It multiplies engine torque to an increasing extent as vehicle speed drops and throttle opening is increased. This has the effect of making the transmission or transaxle more responsive and reduces the amount of shifting required.,Drive plate 2. Converter lockup clutch 3.Torque converter
6、 P. Impeller R. Stator T. Turbine 4.Clutch A 5. Clutch B 6. Clutch C 7. Clutch C 8. Clutch D 9. Planetary gear set 10. Planetary gear set, fourth gear 11. Clutch E 12. Clutch F 13. Output 14-17. One-way clutch Fig. 9-1 Components of a typical automatic transmission,The torque converter is a metal ca
7、se which is shaped like a sphere that has been flattened on opposite sides, it is bolted to the rear end of the engines crankshaft. Generally, the entire metal case rotates at engine speed and serves as the engines flywheel. The case contains three sets of blades (Fig.9-2). One set is attached direc
8、tly to the case. This set forms the torus or pump. Another set is directly connected to the output shaft, and forms the turbine. The third set is mounted on a hub which, in turn, is mounted on a stationary shaft through a one-way clutch. This third set is known as the stator. A pump, which is driven
9、 by the converter hub at engine speed, keeps the torque converter full of automatic transmission fluid at all times. Fluid flows continuously through the unit to provide cooling. Under low speed acceleration, the torque converter functions as follows: The torus is turning faster than the turbine. It
10、 picks up fluid at the center of the converter and, through centrifugal force, slings it outward. Since the outer edge of the converter moves faster than the portions at the center, the fluid picks up speed.,Fig. 9-2 The torque converter housing is rotated by the engines crankshaft, and turns the im
11、peller. The impeller then spins the turbine, which gives motion to the turbine shaft, driving the gears,The fluid then enters the outer edge of the turbine blades; it then travels back toward the center of the converter case along the turbine blades. In impinging upon the turbine blades, the fluid l
12、oses the energy picked up in the torus.,If the fluid was now returned directly into the torus, both halves of the converter would have to turn at approximately the same speed at all times, and torque input and output would both be the same. In flowing through the torus and turbine, the fluid picks u
13、p two types of flow, or flow in two separate directions. It flows through the turbine blades, and it spins with the engine. The stator, whose blades are stationary when the vehicle is being accelerated at low speeds, converts one type of flow into another 2. Instead of allowing the fluid to flow str
14、aight back into the torus, the stators curved blades turn the fluid almost 90 toward the direction of rotation of the engine. Thus the fluid does not flow as fast toward the torus, but is already spinning when the torus picks it up. This has the effect of allowing the torus to turn much faster than
15、the turbine. This difference in speed may be compared to the difference in speed between the smaller and larger gears in any gear train. The result is that engine power output is higher, and engine torque is multiplied.,As the speed of the turbine increases, the fluid spins faster and faster in the
16、direction of engine rotation. As a result, the ability of the stator to redirect the fluid flow is reduced. Under cruising conditions, the stator is eventually forced to rotate on its one-way clutch in the direction of engine rotation. Under these conditions, the torque converter begins to behave almost like a solid shaft, with the torus and turbine speeds being almost equal. PLANETARY GEAR The ability of the torque converter to m
