Power train for automatic transmissions

Details Power train for automatic transmissions Power train for automatic transmissions

2000-12-21

2002-10-22

Wright, Dirk (Department: 3681)

Planetary gear transmission systems or components

With means to vary drive ratio or disconnect drive

Plural elements selectively braked

C475S280000, C475S281000, C475S285000, C475S286000, C475S287000, C192S048920

Reexamination Certificate

active

06468177

ABSTRACT:

BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a power train for an automatic transmission used in vehicles. More particularly, the invention relates to a power train for a 4-forward speed and 1-reverse speed automatic transmission.
(b) Description of the Related Art
Generally, automatic transmission systems for vehicles are provided with a transmission control unit (TCU) which automatically controls shift ratios according to changes in a running condition of the vehicle.
The typical TCU controls a plurality of friction elements provided in a gear train to either operative or inoperative states to select one of the three essential elements of a planetary gear set (i.e., a sun gear, a ring gear, or a planet carrier) to be an input element, a reaction element, or an output element, thereby controlling an output number of revolutions.
Particularly, a power train that can realize 4-forward speeds and 1-reverse speed comprises a plurality of heavy and large-sized clutches and brakes and a plurality of situationally inoperative friction elements.
FIG. 3
shows such a conventional power train.
The conventional power train includes first and second single pinion planetary gear sets
208
and
210
. The first single pinion planetary gear set
208
includes a first sun gear
216
, a first planet carrier
212
, and a first ring gear
218
. The second single pinion planetary gear set
210
includes a second sun gear
220
, a second planet carrier
222
, and a second ring gear
224
.
Rotation power of an engine (not shown) is transmitted to an input shaft
206
via a torque converter
204
, then is further transmitted to the first and second single planetary gear sets
208
and
210
, and finally output through a transfer drive gear
214
connected to the first planet carrier
212
. The shifting operation is realized while the rotation power of the engine passes through the first and second single planetary gear sets
208
and
210
.
The first planet carrier is fixedly connected to the second ring gear
224
and the first sun gear
216
is variably connected to the input shaft
206
with a first clutch C
1
interposed therebetween. The first clutch C
1
is operated in all of the forward speed ratios.
The second planet carrier
222
is variably connected to the input shaft
206
with a second clutch C
2
interposed therebetween, and the second sun gear
220
is variably connected to the input shaft
206
with a third clutch C
3
interposed therebetween. The second clutch C
2
is operated in third and fourth forward speed ratios, and the third clutch C
3
is operated in a reverse range.
In addition, the second planet carrier
222
is fixedly connected to the first ring gear
218
, and the combination of the second planet carrier
222
and the first ring gear
218
is connected to the transmission housing
226
with a first brake B
1
interposed therebetween. The second sun gear
220
is connected to the transmission housing
226
with a second brake B
2
interposed therebetween.
The power output through the transfer drive gear
214
is dispensed to a drive shaft through an intermediate shaft
228
and a differential
230
.
In the above described prior power train, since the first clutch, the first brake, and the second brake are arranged such that they are spaced away from each other in an axial direction of the transmission housing, the longitudinal length of the housing is increased, limiting space for disposing one-way clutches which are used for improving shift quality.
SUMMARY OF THE INVENTION
Therefore, the present invention has been made in an effort to solve the above problems.
It is an objective of the present invention to provide a power train for an automatic transmission that is lightweight and compact in size, while at the same time providing improved power efficiency.
To achieve the above object, the present invention provides a power train for an automotive automatic transmission comprising a first planetary gear having a plurality of operating elements; a second planetary gear having a plurality of operating elements, at least one of the operating elements of the second planetary gear being fixedly connected to one of the operating elements of the first planetary gear; and a plurality of clutches, brakes, and one-way clutches for variable connecting elements of the first and second planetary gears to an input shaft, a transmission housing, or to each other, wherein at least two of the clutches are arranged spaced away from each other in a radial direction of the input shaft.
At least two of the brakes share a single retainer with each other, and one of the two clutches arranged spaced away from each other in a radial direction of the input shaft has a piston functioning as a retainer of the other of the two clutches.
The two clutches arranged spaced away from each other in a radial direction of the input shaft share a single spring with each other.
The plurality of operating elements of the first planetary gear comprise a first sun gear, a first planet carrier, and a first ring gear; the plurality of operating elements of the second planetary gear comprise a second sun gear, a second planet carrier, and a second ring gear; the first planet carrier is fixedly connected to the second ring; the plurality of clutches comprise first, second and third clutches for variably connecting the first sun gear, the second planet carrier, and the second sun gear to the input shaft, respectively, and a fourth clutch for variable connecting the second planet carrier to the first ring gear; the plurality of brakes comprise first and second brakes for connecting the second planet carrier and the second sun gear to the transmission housing; the plurality of one-way clutches comprise first and second one-way clutches for connecting the second planet carrier to the ring gear and the transmission housing; and the second and third clutches are the two clutches arranged spaced away from each other in a radial direction of the input shaft.
According to another aspect, the present invention provides an automotive automatic transmission comprising a first planetary gear having a plurality of operating elements; a second planetary gear having a plurality of operating elements, at least one of the operating elements of the second planetary gear being fixedly connected to one of the operating elements of the first planetary gear; and a plurality of clutches, brakes, and one-way clutches for variable connecting elements of the first and second planetary gears to an input shaft, a transmission housing, or to each other, wherein inner and outer races of the respective first and second one-way clutches of the plurality of one-way clutches share a single member with each other.
An outer race of the first one-way clutch is connected to the transmission housing by a spline.
The outer race of the second one-way clutch functions as a retainer of at least one of the brakes.
The inner and outer races of the respective first and second one-way clutches are separately formed and splined to each other to form the single member.
At least two of the clutches are arranged spaced away from each other in a radial direction of the input shaft.


REFERENCES:
patent: 4607541 (1986-08-01), Miura et al.
patent: 5006102 (1991-04-01), Takase et al.
patent: 5879263 (1999-03-01), Haka
patent: 6024197 (2000-02-01), Suwa et al.
patent: 6200242 (2001-03-01), Coffey

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