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本帖最后由 白马啸西枫 于 2009-12-31 21:24 编辑 % R7 ?- H8 l2 w+ |6 D
7 E; X, e1 M& c R( S: n 22# 小黄 2 [: t! k3 H2 t( y3 Z6 h$ X; U& i3 n
% ]8 I, ?8 `9 X/ E- t! n小黄,你说得对,但不全面。& j" F+ x' y1 K5 J; _
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:
$ m$ h7 v4 l( K) G+ I以下摘自维基百科:8 D7 e5 \$ T% O$ f, o$ v4 c
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。
) A& C) {# O3 DA unit with a planetary gearset which turns the driveshaft faster than the transmission output shaft.
1 Z5 }* l' i- e1 _/ o* O+ v3 _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& F- z+ ^. U* s+ l7 p+ l- \' P
Gearing 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.
7 z n' l3 y6 z9 M$ D2 `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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