Planetary gear transmission systems or components – With means to vary drive ratio or disconnect drive – Plural elements selectively braked
Reexamination Certificate
1999-12-17
2001-08-14
Lorence, Richard M. (Department: 3681)
Planetary gear transmission systems or components
With means to vary drive ratio or disconnect drive
Plural elements selectively braked
C475S313000
Reexamination Certificate
active
06273838
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 5-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 5-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, the gear train comprising a first planetary gear set having a first element variably connected to an input shaft and a transmission housing, a second element variably connected to the input shaft and the transmission housing, and a third element connected to a transfer shaft to transmit power to the transfer shaft, a second planetary gear set having a fourth element connected to the transfer shaft to transmit power to the transfer shaft, a fifth element variably connected to the input shaft, and a sixth element fixedly connected to the second element to provide a combination element, the combination element being variably connected to the input shaft, and friction means for variably connecting the first, second, fifth, and sixth elements to either the input shaft or the transmission housing.
Preferably, the first and second planetary gear sets are double pinion planetary gear sets.
Preferably, the first element is a first sun gear, the second element is a first planet carrier, the third element is a first ring gear, the fourth element is a second planet carrier, the fifth element is a second sun gear, and the sixth element is a second ring gear.
Preferably, the friction means comprise a first clutch disposed between the input shaft and the second sun gear, a second clutch disposed between the input shaft and the combination of the first planet carrier and the second ring gear, a third clutch disposed between the input shaft and the first sun gear, a first brake disposed between the transmission housing and the first sun gear, and a second brake disposed between the first planet carrier and the transmission housing.
In the above described inventive gear train, a first speed is realized by operating the first clutch and the first brake, a second speed is realized by operating the second clutch and the first brake, a third speed is realized by operating the first and second clutches, a fourth speed is realized by operating the second and third clutches, a fifth speed is realized by operating the first and third clutches, and a reverse speed is realized by operating the first clutch and the second brake.
REFERENCES:
patent: 3010343 (1961-11-01), Orr et al.
patent: 4483215 (1984-11-01), Ishimaru et al.
patent: 0305045 (1989-01-01), None
patent: 59-126139 (1984-07-01), None
patent: 02-107863 (1990-04-01), None
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hyundai Motor Company
Lorence Richard M.
Parekh Ankur
LandOfFree
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