Hybrid powertrain unit for motor vehicles with a device for transmission to a further axle of the motor vehicle

A hybrid powertrain unit for a motor vehicle, comprising:

• an internal-combustion engine;
• a gearbox device including:
• at least one primary shaft, that can be connected to a shaft of the internal-combustion engine by a clutch device;
• at least one secondary shaft, an axis of which is parallel to and at a distance from an axis of said at least one primary shaft and which carries an output pinion;
• a plurality of pairs of gears corresponding to a plurality of forward gear ratios, in which one of the gears of each pair of the plurality of pairs of gears is rigidly connected in rotation with respect to one of said at least one primary and secondary shafts and the other is freely rotatable with respect to the other of said at least one primary and secondary shafts;
• and
• a plurality of gear-selection devices for coupling in rotation each of said freely rotatable gears with the shaft on which it is mounted;
• a differential, having a first crown wheel meshing with said output pinion of said at least one secondary shaft of the gearbox device;
• an electric machine adapted to operate both as an electric motor and as an electric generator and having a casing rigidly connected to a supporting structure of said powertrain unit, and a shaft connected by a transmission to a second crown wheel of said differential;
• an engagement device arranged, in said transmission, between the shaft of the electric machine and the second crown wheel of the differential;
• and
• an actuator arrangement for actuating said engagement device;
• wherein the shaft of the electric machine is connected to the shaft of the internal-combustion engine at an end thereof opposite to an end connected to the gearbox device;
• and
• wherein said transmission that connects the shaft of the electric machine to said second crown wheel of the differential includes a gear for driving a transmission shaft connected to a further axle of the vehicle different than an axle associated with two output shafts of the differential.