Two-speed transmission for electric vehicles

A two-speed transmission for electric vehicles provided with an electric machine able to operate alternatively as a motor according to a traction operating mode or as a generator according to a regeneration operating mode, the transmission comprising:

• a primary shaft;
• a secondary shaft;
• a gearing of first speed, or low speed, comprising a first driving gearwheel carried by the primary shaft and a first driven gearwheel carried by the secondary shaft and permanently meshing with the first driving gearwheel;
• a gearing of second speed, or high speed, comprising a second driving gearwheel carried by the primary shaft and a second driven gearwheel carried by the secondary shaft and permanently meshing with the second driving gearwheel;
• an overrunning clutch associated to said first driven gearwheel to allow the transmission of the torque via the gearing of first speed only in the direction from the primary shaft to the secondary shaft;
• a first coupling device selectively coupling said second driving gearwheel for rotation with the primary shaft, said first coupling device being shiftable between an open condition and a closed condition;
• and
• a second coupling device selectively coupling said first driven gearwheel, namely the gearwheel to which the overrunning clutch is associated, for rotation directly with the secondary shaft, said second coupling device being shiftable between an open condition and a closed condition;
• characterized in that said first coupling device is normally closed and is shiftable between the open condition and the closed condition independently of the open or closed condition of said second coupling device.