| 摘要 |
The transmission comprises: a primary shaft (12); a secondary shaft (14); a gear set of first gear comprising a first driving gearwheel (16) and a first driven gearwheel (22), wherein the first driven gearwheel (22) comprises a hub (28) rigidly connected for rotation with the secondary shaft (14) and a ring gear (26) mounted around the hub (28) so as to be able to rotate relative to this latter; a gear set of second gear comprising a second driving gearwheel (18) and a second driven gearwheel (24); an overrunning clutch (30) interposed between the ring gear (26) and the hub (28) of the first driven gearwheel (22) to allow the transmission of the torque through the gear set of first gear only in the direction from the primary shaft (12) to the secondary shaft (14); a first coupling device (32) arranged to connect the ring gear (26) of the first driven gearwheel (22) directly for rotation with the secondary shaft (14) so as to allow the transmission of the torque through the gear set of first gear also in the direction from the secondary shaft (14) to the primary shaft (12); and a second coupling device (44) arranged to connect the second driving gearwheel (18) or the second driven gearwheel (24) for rotation with the respective shaft (12, 14). The first coupling device (32) comprises a hub (34) and a sliding sleeve (38) provided with first engagement teeth (40) arranged to mesh with second engagement teeth (42) of the ring gear (26) of the first driven gearwheel (22), the sliding sleeve (38) being connected for rotation with the respective hub (34) and being axially slidable relative to this latter between a disengagement position, in which the first and second engagement teeth (40, 42) are disengaged from each other, and an engagement position, in which the first and second engagement teeth (40, 42) mesh with each other. The transmission further comprises connection means (36), which connect the hub (28) of the first driven gearwheel (22) for rotation with the hub (34) of the first coupling device (32), thereby allowing these hubs (28, 34) to rotate relative to each other about the axis of the respective shaft (14) between two end-of-travel positions, and elastic means (48) interposed between these hubs (28, 34) to apply on these latter a biasing torque tending to urge them towards one of these end-of-travel positions. |
