Planetary gear transmission systems or components – Variable speed or direction transmission combined with... – Variable speed or direction is planetary transmission
Patent
1995-08-15
1997-07-01
Marmor, Charles A.
Planetary gear transmission systems or components
Variable speed or direction transmission combined with...
Variable speed or direction is planetary transmission
475275, 475276, 475277, 475278, 475279, F16H 300, F16H 3700
Patent
active
056431309
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns a power train of an automatic transmission for a vehicle.
Generally, an automatic transmission for a vehicle includes a transmission control unit which automatically controls a plurality of clutches and brakes mounted in a gear train so as to adjust the gear ratio of planetary gears according to the speed and load. While a power train must normally include a compound planetary gear unit and at least five friction elements in order to produce four-forward speed ratio and one-reverse speed ratio, to improve the shifting operation more effectively, a compound planetary gear unit including seven friction elements and three one-way clutches is required. This results in a complicated construction of the power train and an increase of the weight.
Further, the conventional automatic transmission comprises a limited number of shift phases, so that shifting shock impulses unavoidably occur and the speed shifting range is also restricted due to the limited number of the gear ratios, thus making it difficult to achieve the optimum ratio of fuel and power performance. Moreover, the shifting shock impulses frequently occur due to the great input torque and frequent shifting operation in the low speed section. In addition, the input shaft and the gear train must be directly connected with each other in the high speed region in order to make the power transmission efficiency better. But the conventional transmission has no such means.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a power train of an automatic transmission for a vehicle with means for making a continuous shift operation in the low speed region so as to reduce the shifting shock impulses.
It is another object of the present invention to provide a power train of an automatic transmission for a vehicle which directly connects a gear train with an output end of an engine so as to improve the power transfer efficiency.
It is still another object of the present invention to provide a power train which can simplify the structure of a power train of an automatic transmission for a vehicle by reducing the number of one-way clutches and friction elements.
According to an embodiment of the present invention, a power train of an automatic transmission for a vehicle comprises: engine; second simple planetary gear units mounted on an input shaft for carrying out a first shift operation, the first simple planetary gear unit including a first sun gear surrounded by and engaged with a plurality of first pinion gears carried by a first planetary carrier, a first ring gear surrounding and internally engaged with the first pinion gears, and a hub connected with the first ring gear, and the second simple planetary gear unit including a second sun gear surrounded by and engaged with a plurality of second pinion gears carried by a second planetary carrier, and a second ring gear surrounding and internally engaged with the second pinion gears; simple planetary gear units for carrying out a second shift operation, the third simple planetary gear unit including a third sun gear surrounded by and engaged with a plurality of third pinion gears carried by a third planetary carrier, and a third ring gear surrounding and internally engaged with the third pinion gears, and the fourth simple planetary gear unit including a fourth sun gear surrounded by and engaged with a plurality of fourth pinion gears carried by a fourth planetary carrier, and a fourth ring gear surrounding and internally engaged with the fourth pinion gears; engine; and a vehicle axle, wherein the first ring gear is selectively locked by a friction element mounted on the transmission housing to serve as an input or reaction element, the second ring gear is connected with the first sun gear selectively locked by a friction element to serve as an input or reaction element, the first and second pinion gears are connected together via a first power transfer member for transferring the gear shift ratio of the first shift part throu
REFERENCES:
patent: 3613479 (1971-10-01), Borneman
patent: 4395925 (1983-08-01), Gaus
patent: 5203749 (1993-04-01), Ito
patent: 5261861 (1993-11-01), Lemieux
Hyundai Motor Company
Jensen Nathan O.
Marmor Charles A.
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