Power train of five-speed automatic transmission for vehicle

Details Power train of five-speed automatic transmission for vehicle Power train of five-speed automatic transmission for vehicle

1996-03-01

1997-12-23

Marmor, Charles A.

Planetary gear transmission systems or components

With means to vary drive ratio or disconnect drive

475204, 475281, 475285, F16H 344

Patent

active

057002231

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a power train for a five-speed automatic transmission of a vehicle, and more particularly, to a power train which can output five forward speed ratios and one reverse ratio.
2. Description of the Related Art
In general, an automatic transmission comprises a planetary gear unit which is connected between a torque converter and a driven shaft.
The planetary gear unit includes a sun gear, a plurality of planet gears, a carrier mounting the planet gears to each other, and a ring gear.
Various clutches, brakes, and friction elements are utilized to selectively operate the gears of the planetary gear unit as reacting force elements or input elements to produce the desired speed ratios.
In a high-powered engine, failing to fully utilize a performance of the engine, the automatic transmission is deteriorated in its fuel consumption ratio, power capability, and driving capability.
Accordingly, in order to fully utilize the performance of the engine, multiple transmission speed ratios have been considered. The transmission having the multiple speed ratios requires that each speed ratio should be easily controlled. Easy control of the speed ratios means that when changing a speed from one speed ratio to another speed ratio, only one of the friction elements is controlled to realize the change of speed ratio.
U.S. Pat. No. 5,112,285 discloses a transmission having multiple transmission speed ratios. However, in this patent, when changing the speed from one speed ratio to another speed ratio, since a friction element which is in an engaged state should be released and another friction element should be engaged, controlling the speed ratio is complicated.


SUMMARY OF THE INVENTION

Accordingly, the present invention has been made in an effort to solve the above-described problem.
It is an object of the present invention to provide a power train of an automatic transmission for a vehicle which can fully utilize a performance of an engine.
It is another object of the present invention to provide a power train of the automatic transmission for the vehicle, which can easily accomplish a transmission control.
To accomplish the above objects, the present invention provides a power train for an automatic transmission of a vehicle, comprising: an input axle for delivering power from an engine; a main-transmission mechanism having a compound planetary gear unit for outputting the power as four speed ratios; a sub-transmission mechanism having a single planetary gear unit for increasing a speed ratio which is output from the main-transmission mechanism as a largest speed ratio of the four speed ratios; the main-transmission mechanism including a first friction element for selectively transmitting the power from the input axle to a first sun gear of the compound planetary gear unit, a second friction element for making a second sun gear of the compound planetary gear unit as an idling element, a third friction element for selectively transmitting the power from the input axle to a planet carrier of the compound planetary gear unit, and a fourth friction element for operating the sun gear as a reacting force element; and the sub-transmission mechanism including a fifth friction element for operating a fifth sun gear of the simple planetary gear unit as the reacting force element.


BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and other advantages of the invention will become apparent from the following description in conjunction with the attached drawings, in which:
FIG. 1 is a schematic diagram showing a power train of an automatic transmission according to a first embodiment of the present invention;
FIG. 2 is a table illustrating an operating sequence of friction elements at each speed ratio of the power train in FIG. 1;
FIG. 3 is a schematic diagram showing a power train of an automatic transmission according to a second embodiment of the present invention; and
FIG. 4 is a table illustrating an operating sequence of friction elements

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