| 摘要 |
PROBLEM TO BE SOLVED: To provide a multi-stage gear train which has superior gear ratio steps by inputting a reduced rotation to a ravigneaux type four-element planetary gear set. SOLUTION: The automatic transmission for a vehicle has a ravigneaux type four element planetary gear set G1, a reduction planetary gear set G3, clutches C-1 and C-2 for controlling the ravigneaux type four-element planetary gear set G1 and the reduction planetary gear set G3, brakes B-1 and B-2, and a means B-3 for inputting the reduced rotation from the reduction planetary gear set G3 to the planetary gear set G1. A long pinion of the planetary gear set is a stepped pinion P1, P2, having a large diameter portion P1 for engaging with a ring gear R1 and a sun gear S1, and a small-diameter portion P2 for engaging with a short pinion P2' engaging with a sun gear S2. According to this method, the step of gear ratios between the reduction steps on both sides of the reduction stage, achieved by inputting the reduced rotation is widened, and a narrow interval in gear ratio steps between specific reduction stages is eliminated. As a result, the gear ratio steps among all the reduction stages become proper.
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