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1、译文题目：Automobile Transmission 汽车变速器学生姓名：学号：0专业：机械设计制造及其自动化（现代汽车技术）所在学院： 机 电 工 程 学 院指导教师：职称：讲 师2012年2月 20 日Automobile TransmissionAs we know , an engine can generate only limited torque at low speeds .Driving condition is very complicated and this required the tractive effort and speed vary in a large
2、 scope .And without sufficient torque , moving a heavily loaded vehicle from a standing start is impossible . In any engine , the crankshaft always rotates in the same direction . If the engine transmitted its power directly to the drive axles , the wheels could be driven only in one direction.Given
3、 a level road ,an automobile without a transmission could be made to move by accelerating the engine and engaging the clutch . However , a start under these conditions would be slow , noisy and uncomfortable . In condition , it would place a tremendous strain on the engine and driving parts of the a
4、utomobile.So in order to get smooth starts and have power to pass and climb hills , a power ratio must be provided to multiply the torque and turning effort of the engine . Also required is a speed ratio to avoid the need for extremely high engine rpm at high road speeds . The transmission is geared
5、 to perform these functions . A transmission is a speed and power changing device installed at some point between the engine and driving wheels of the vehicle . It is designed for changing the torque transmitted form the engine crankshaft to the propeller shaft , reversing the vehicle movement and d
6、isengaging the engine from the drive line for a long time at parking or coasting . A higher torque should be applied to the wheels to set an automobile in motion or move uphill with a full load than to keep it rolling after it gets under way on level stretches of the road , when inertia is high and
7、tractive resistance is low . To meet these variable torque requirement , special gear boxes are used . Such gear boxes are called fixedratio transmissions . The transmission consists of a housing , an input shaft and gear , an output shaft and gear , an idler shaft , a reverse gear , a cluster of ge
8、ars and a gear shift mechanism . The housing is cast of iron which has upper and side covers and bores for the installation of shafts . The bottom and side walls are provided with holes for filling and draining oil . The input shaft is made of steel integral with the driving gear and the rim . The f
9、ront end of the input shaft is installed on the bearing in the bore of the crankshaft , while the rear end rotates in the bore of the front wall of the housing . The input shaft is arranged so that only the driving gear and the rim are accommodated inside the housing while the splined portion of the
10、 shaft protruding from the transmissions carries the hub of the clutch driven disk . The output shaft is splined and rests with its front end on a roller bearing installed in the bore of the input shaft . The other end of the output shaft rotates in a ball bearing in the transmission housing wall .
11、The output shaft splines carry the sliding gear . The output shaft is coaxial with the input shaft . The idler shaft carries a cluster of gears of different sizes . The cluster is mounted in the roller bearings on an axle or , together with the shaft , on bearings in the housing wall bores . The idl
12、er shaft constantly rotates with the input shaft because their gear in constant mesh . The reverse gear rotates on an axle secured in the holes of the housing walls .The gear shift mechanism is designed for engaging gears , setting them neutral and engaging the reverse speed . The speeds are changed
13、 by shifting the gear or sleeves along the output shaft . The transmission type depends on the number of the sliding gears or sleeves . The transmission with two sliding gears or synchronizer sleeves is called two-range , with three gears ,three-range . Depending on the number of forward speeds ther
14、e are three , four and five-speed transmission . The gear shift mechanism is mounted on the top cover . The shift lever is arranged on the cover or on the bracket of the lever support . The transmission gear are shifted by means of a gear shift mechanism . The gear shift mechanism consists of a leve
15、r , shift rails , shift forks , retainers , locks and a reverse speed safety device . The shift lever mounted on the transmission cover has a spherical bulb housed in a socket in the cover boss . A pin keeps the lever against rotation . The cover drillings accommodate shift rails which carry the shi
16、ft forks and shift blocks with slots . The lower end of the lever enters the slots of the shift blocks . The forks fit into the grooves of the sliding gears and synchronizer sleeves . To change a speed , the upper end of the lever is slid to a certain position , the lower end of the lever moves the shift block and the latter pushes the shift rail with the fork and gear until the required speed is engaged . Retainers
