Planetary gear transmission systems or components – With means to vary drive ratio or disconnect drive – Plural elements selectively braked
Reexamination Certificate
1999-12-17
2001-08-07
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
With means to vary drive ratio or disconnect drive
Plural elements selectively braked
Reexamination Certificate
active
06270441
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a gear train for an automatic transmission used in vehicles. More particularly, the invention relates to a gear train for a 6-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 planetary carrier) to be an input element, a reaction element, or an output element, thereby controlling an output number of revolutions.
Particularly, a gear train that can realize 6-forward speeds and 1-reverse speed comprises a plurality of heavy and large-sized clutches and brakes and a plurality of inoperative friction elements, resulting in deterioration of power and space efficiencies.
SUMMARY OF THE INVENTION
Therefore, the present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a gear 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 gear train for an automatic transmission a first planetary gear set comprising a first element variably connected to an input shaft, a second element variably connected to the first element, the input shaft and a transmission housing, and a third element connected to a transfer shaft to transmit power the transfer shaft, a second planetary gear set comprising a fourth element variably connected to the input shaft and the transmission housing, a fifth element fixedly connected to the first element of the first planetary gear set, and a sixth element connected to the transfer shaft to transmit power to the transfer shaft; and friction means for variably connecting the first, second, and fourth element to either the input shaft or the transmission housing.
Preferably, the first planetary gear set is a single pinion planetary gear set. The first element is a sun gear, the second element is a ring, and the third element is a carrier.
Preferably, the second planetary gear set is a single pinion planetary gear set. The fourth element is a sun gear, the fifth element is a ring gear, and the sixth element is a carrier.
As the friction means, a first clutch is interposed between the input shaft and the combination of the first sun gear and the second ring gear, a second clutch is interposed between the second sun gear and the input shaft, a third clutch is interposed between the first ring gear and the input shaft. In addition, a first brake is interposed between the first ring gear and the transmission housing, and a second brake is interposed between the transmission housing and the second sun gear.
A first speed is realized by operating the first clutch and the first brake, a second speed is realized by operating the first clutch and the second brake, a third speed is realized by operating the first and second clutches, a fourth speed is realized by operating the first and third clutches, a fifth speed is realized by the second and third clutches, a sixth speed is realized by operating the third clutch and the second brake, and a reverse speed is realized by operating the second clutch and the first brake.
REFERENCES:
patent: 5890988 (1999-04-01), Kasuya et al.
patent: 5997429 (1999-12-01), Raghavan et al.
patent: 6146305 (2000-11-01), Hebbale et al.
patent: 0305045 (1989-01-01), None
patent: 62-93544 (1987-04-01), None
patent: 64-12160 (1989-01-01), None
patent: 1-55454 (1989-03-01), None
patent: 4-15338 (1992-01-01), None
patent: 4-25648 (1992-01-01), None
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hyundai Motor Company
Marmor Charles A
Parekh Ankur
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