| 摘要 |
The transmission comprises: a primary shaft (12); a secondary shaft (14); a gearing of first speed comprising a first driving gearwheel (16) carried by the primary shaft (12) and a first driven gearwheel (24) carried by the secondary shaft (14) and permanently meshing with the first driving gearwheel (16); a gearing of second speed comprising a second driving gearwheel (18) carried by the primary shaft (12) and a second driven gearwheel (26) carried by the secondary shaft (14) and permanently meshing with the second driving gearwheel (18); an overrunning clutch (32) associated to one (24) of the first driving gearwheel (16) and first driven gearwheel (24) to allow the transmission of the torque via the gearing of first speed only in the direction from the primary shaft (12) to the secondary shaft (14); a first coupling device (34) arranged to connect either (24) of the first driving gearwheel (16) and first driven gearwheel (24), namely the gearwheel (24) to which the overrunning clutch (32) is associated, for rotation directly with the respective shaft (14), so as to allow the transmission of the torque via the gearing of first speed also in the direction from the secondary shaft (14) to the primary shaft (12); and a second coupling device (22) arranged to connect either (18) of the second driving gearwheel (18) and second driven gearwheel (26) for rotation with the respective shaft (12). The first and second coupling devices (34, 22) are both shiftable between an open condition and a closed condition independently of each other. The first coupling device (34) is normally open, whereas the second coupling device (22) is normally closed. |
