| 摘要 |
PURPOSE: A power train of a 6-speed automatic transmission for a vehicle and a shift control method are provided to improve fuel consumption by increasing ratio between gear levels, to mainly control a brake in shifting, to improve shift quality by simultaneously controlling main and sub shift units in shift except for 2- to 3-speed and 3- to 2-speed, and to enhance durability to integrally operate the sub shift unit in forward 3-,4-,5-, and 6-speed. CONSTITUTION: A power train of a 6-speed automatic transmission for a vehicle is composed of a main shift unit(M) and a sub shift unit(S). The main shift unit comprises the combination of first and second single pinion planetary gear sets(2,4) at an input shaft(10), fixably connects a first planetary carrier(12) operated as an output element with a second ring gear(16) and a first ring gear(18) with a second planetary carrier(20), variably connects a first sun gear(22), the second planetary carrier, and a second sun gear(24) to the input shaft, respectively, variably fixes a connecting member(26) for connecting the first ring gear with the second planetary carrier to a housing(28), and variably fixes the second sun gear to the housing. The sub shift unit comprises the combination of third and fourth single pinion planetary gear sets(6,8) at an output shaft parallel to the input shaft, connects a third ring gear(40) to an output element of the main shift unit, fixably connects third and fourth sun gears(30,32), fixably connects a third planetary carrier(34) operated as the output element with a fourth ring gear(36), variably connects the third and fourth sun gears, and variably connects a fourth planetary carrier(42) with the housing.
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