 鲜花( 242)  鸡蛋( 8)
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本帖最后由 白马啸西枫 于 2009-12-31 21:24 编辑
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+ S, i# u2 N3 z/ ~& A2 ^3 \* l' A. S 22# 小黄 , ?. w0 ~9 o! i7 {3 R3 ?
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小黄,你说得对,但不全面。& ~& H8 ~5 _9 `' C) v
overdrive 档是汽车的最高档,也叫超速挡,超比档,正如shark 27所说: 此时的引擎曲轴转一圈时,齿轮箱的输出轴却可转超过一圈。对引擎而言,就是输出轴端的扭力变小了:
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/ D) U9 R/ I; Q1 Y3 k+ R% M8 t: Y超比(省油)档开关(O/D):自动变速器的最高档通常是超比档,该档位齿轮比(减速比)低于一,也就是该档位将引擎扭力放大倍数变成低于一倍,有助于省油,但不利于加速。超比开关关闭后,D档行驶时,自动变速器将无法换入超比档。通常在上坡及路面状况不良时应考虑将此开关关闭。+ ~! H- D- J/ H& G
A unit with a planetary gearset which turns the driveshaft faster than the transmission output shaft.7 l1 `" E8 a0 K+ u" W
An additional gearbox which is mounted in the driveline. Normally the final drive ratio is 1:1; but the overdrive makes it less (e.g., 0.87:1). The overdrive can reduce gas consumption at sustained high-speed driving, engine noise, and engine wear. Also called "overdrive transmission." Also see aftermarket overdrive
& B C6 k* K, pGearing in which less than one revolution of a transmission's input shaft causes one turn of the output shaft. The purpose of overdrive is to reduce engine rpm in high gear for better fuel economy. Example: A transmission with an overdrive top gear has a ratio of 0.70 to one. Turning the input shaft 0.7 revolutions causes 1.0 revolution of the output shaft.5 K1 [9 Q! o$ h! @2 `5 i
因为输出轴端的扭距变小,所以变速箱的设计师有意将其设计成超车时踩油会降档,以提高变速箱输出端的扭距离和加速度,从而使汽车更快地加速。 |
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