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PPT研究院 POWERPOINT ACADEMY * * AUTOMOTIVE TRANSMISSION The shaft is suspended by the main bearings, and is split towards the input end. At the point of the split, a pilot bearing holds the shafts together. The gears and clutches ride on the mainshaft, the gears being free to turn relative to the mainshaft except when engaged by the clutches. * AUTOMOTIVE TRANSMISSION ?2. Automatic Transmission Most modern North American, and many larger, high specification German cars have an automatic transmission that will select an appropriate gear ratio without any operator intervention. They primarily use hydraulics to select gears, depending on pressure exerted by fluid within the transmission assembly. * AUTOMOTIVE TRANSMISSION Rather than using a clutch to engage the transmission, a fluid flywheel, or torque converter is placed in between the engine and transmission. It is possible for the driver to control the number of gears in use or select reverse, though precise control of which gear is in use may or may not be possible. * AUTOMOTIVE TRANSMISSION Automatic transmissions are easy to use. In the past, automatic transmissions of this type have had a number of problems. * AUTOMOTIVE TRANSMISSION They were complex and expensive, sometimes had reliability problems (which sometimes caused more expenses in repair), have often been less fuel-efficient than their manual counterparts (due to slippage in the torque converter), and their shift time was slower than a manual making them uncompetitive for racing. With the advancement of modern automatic transmissions this has changed. * AUTOMOTIVE TRANSMISSION Since their inception, automatic transmissions have been very popular in the United States, and some vehicles are not available with manual gearboxes anymore. In Europe automatic transmissions are gaining popularity as well. * AUTOMOTIVE TRANSMISSION Attempts to improve the fuel efficiency of automatic transmissions include the use of torque converters which lock up beyond a