Planetary gear transmission systems or components – With means to vary drive ratio or disconnect drive – Carrier braked
Reexamination Certificate
1999-12-17
2001-05-15
Marmor, Charles A. (Department: 3681)
Planetary gear transmission systems or components
With means to vary drive ratio or disconnect drive
Carrier braked
Reexamination Certificate
active
06231471
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 the planetary gear set (a sun gear, a ring gear and a planet carrier) to be an input element, one to be a reaction element, and one to be an output element, thereby controlling an output number of revolutions.
Particularly, a gear train that can realize a 5-forward speed and a 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, which is compact in size and light in weight, while providing improved power efficiency.
To achieve the above object, the present invention provides a gear train for an automatic transmission comprising a first planetary gear set comprising a first element variably connected to an input shaft, a second element variably connected to the input shaft and the first element, and a third element connected to a transfer shaft to transmit power to the transfer shaft; a second planetary gear set comprising a fourth element fixedly connected to the first element while being variably connected to the input shaft, a fifth element variably connected to the input shaft while being variably connected to a combination of the first and fourth elements, and a sixth element connected to the transfer shaft to transmit power to the transfer shaft; a third planetary gear set comprising a seventh element fixedly connected to the combination of the first and fourth elements, an eighth element variably connected to the transmission housing, and a ninth element fixedly connected to the third element while being connected to the transfer shaft to transmit power thereto; and friction means for realizing the variable connections.
Preferably, the first planetary gear set is a single pinion planetary gear set, the second planetary gear set is a double pinion planetary gear set, and the third planetary gear set is a single pinion planetary gear set.
Preferably, the first element is a first sun gear, the second element is a first ring gear, the third element is a first planet carrier, the fourth element is a second sun gear, the fifth element is a second planet carrier, the sixth element is a second ring gear, the seventh element is a third sun gear, the eighth element is a third planet carrier, and the ninth element is a third ring gear.
The friction means comprises a first clutch interposed between the input shaft and the second carrier, a second clutch interposed between the input shaft and the first planet carrier, a third clutch interposed between the input shaft and the combination of the first and second sun gears, a first brake interposed between the third planet carrier and the transmission housing.
REFERENCES:
patent: 2-150533 (1990-06-01), None
patent: 2-154846 (1990-06-01), None
patent: 4-29651 (1992-01-01), None
patent: 8-105498 (1996-04-01), None
patent: 11-166598 (1999-06-01), None
Finnegan Henderson Farabow Garrett & Dunner LLP
Hyundai Motor Company
Marmor Charles A.
Parekh Ankur
LandOfFree
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