| 摘要 |
A multiple-speed automatic transmission comprises a first epicyclic gear unit 30, which may be a compound epicyclic, and a second Ravigneaux gear unit 32 having a sun gear 44 that may be connected to an input 28 by a fourth clutch 72. The first gear unit 30 has a sun gear 34 that is fixed to the input 28 and drives ring gear 36, via first and second planet pinion 39, 40, with a gear ratio that is greater than unity. Ring gear 36 may be connected to either sun gear 42 by a first clutch 62 or to sun gear 44 by a second clutch 64 while planet carrier 50 is connect to and disconnected from the input 28 by a third clutch 70. The sun gear 44 is held against rotation, on transmission case 39, by a first brake 66 and the carrier 50 is held against rotation by a second brake 68. By selectively engaging and disengaging the first, second, third and fourth clutches, 62-72 and the first and second brakes 66, 68 a number of gear ratios may be produced. |
