【正文】 ly mounted to the back of the engine and is located under the hump in the center of the floorboard alongside the gas pedal position. A drive shaft connects the rear of the transmission to the final drive which is located in the rear axle and is used to send power to the rear wheels. Power flow on this system is simple and straight forward going from the engine, through the torque converter, then through the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear wheels. On a front wheel drive car, the transmission is usually bined with the final drive to form what is called a transaxle. The engine on a front wheel drive car is usually mounted sideways in the car with the transaxle tucked under it on the side of the engine facing the rear of the car. Front axles are connected directly to the transaxle and provide power to the front wheels. In this example, power flows from the engine, through the torque converter to a large chain that sends the power through a 180 degree turn to the transmission that is along side the engine. From there, the power is routed through the transmission to the final drive where it is split and sent tothe two front wheels through the drive axles. There are a number of other arrangements including front drive vehicles where the engine is mounted front to back instead of sideways and there are other systems that drive all four wheels but the two systems described here are by far the most popular. A much less popular rear drive arrangement has the transmission mounted directly to the 本科生畢業(yè)設(shè)計（論文）38final drive at the rear and is connected by a drive shaft to the torque converter which is still mounted on the engine. This system is found on the new Corvette and is used in order to balance the weight evenly between the front and rear wheels for improved performance and handling. Another rear drive system mountseverything, the engine, transmission and final drive in the rear. This rear enginearrangement is popular on the Porsche.Transmission Components The modern automatic transmission consists of many ponents and systems that are designed to work together in a symphony of clever mechanical, hydraulic and electrical technology that has evolved over the years into what many mechanically inclined individuals consider to be an art form. The cyeloid driveThe cyeloid drive has the essential advnatages sueh as Wide rnage of tranmsission ratio， eompact surtcture，high relibaility nad long wokrnig lief，So It gets borad application and its rsearch goes deep eonstnatly. The drive has been not only applied to traditionalt rnasmissionfield but also has alluring applieation in the aspeets of micro machine，robot gear ,preeision machine taansmission，super mini cycloid drive， asrtonaut cquipment，measurment apparatus，tenement intelligence and hightech equipment. In the family of the cycloid drive，the AFcycloid 一 pin wheel plnaetary driver educer is a new .Trnasmission with the mon cycloid drive，it has a series of advantages such as small volume，lihgtweight，wide range of tranmsission，diversity transmission，long lief time，high rigidiyt，high slewing precision，stbale preeision，high effieiency and stable design of the drive daopts a lot of advnaced theories and technology methoods and uses a kind of innovation stureurte，so the FA drive has overe the defect of the traditional surtcture，enhnaccd the transmissin efficency，volume,and the transmission precision. Automatic transmissions contain many gears in various binations. In a manual transmission, gears slide along shafts as you move the shift lever from one position to another, engaging various sized gears as required in order to provide the correct gear ratio. In an automatic transmission, however, the gears are never physically moved and are always engaged to the same gears. This is acplished through the use of plaary gear sets. One example of a way that this system can be used is by connecting the ring gear 本科生畢業(yè)設(shè)計（論文）39to the input shaft ing from the engine, connecting the pla carrier to the output shaft, and locking the sun gear so that it can39。t move. In this scenario, when we turn the ring gear, the plas will walk along the sun gear (which is held stationary) causing the pla carrier to mm the output shaft in the same direction as the input shaft but at a slower speed causing gear reduction (similar to a car in first gear). If we unlock the sun gear and lock any two elements together, this will cause all three elements to turn at the same speed so that the output shaft will mm at the same rate of speed as the input shaft. This is like a car that is in third or high gear. Another way that we can use a Plaary gear set is by locking the pla carrier from moving, then applying power to the ring gear which will cause the sun gear to turn in the opposite direction giving us reverse gear. The clutch pack is used, in this instance, to lock the pla carrier with the sun gear forcing both to turn at the same speed. If both the clutch pack and the band were released, the system would be in neutral. Turning the input shaft would turn the pla gears against the sun gear, but since nothing is holding the sun gear, it will just spin free and have no effect on the output shaft. To place the unit in first gear, the band is applied to hold the sun gear from moving. To shift from first to high gear, the band is released and the clutch is applied causing the output shaft to turn at the same speed as the input shaft. Many more binations are possible using two or more plaary sets connected in various ways to provide the different forward speeds and reverse that are found in modem automatic transmissions. Some of the clever gear arrangements found in four and now, five, six and even sevenspeed automatics are plex enou