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本帖最后由 白马啸西枫 于 2009-12-31 21:24 编辑 ( p/ |4 }; l) ^. N, l/ p6 X* G% d
7 t! R& _; f0 Y Y 22# 小黄 : g! d& M( D: c D/ R
" a& N, c% `* c5 ~% |& \6 P小黄,你说得对,但不全面。- @% U4 N8 M4 m/ O# b/ m
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:" f- ^. X* O$ O m3 Y# H/ T! H0 G
以下摘自维基百科:
# Z' h' t) {( p: h6 C m! h2 \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。 K" F2 Z; m% c4 v$ N$ A
A unit with a planetary gearset which turns the driveshaft faster than the transmission output shaft.5 i* \, j9 `3 I
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 overdrive9 ]# t9 r* c' h% L
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.
. f1 G. s, L+ A2 Z0 J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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