Hybrid drive system with multiple drive machines

A method of operating a hybrid drive system for a vehicle, comprising:

• transmitting torque provided by an irreversible drive machine coupled to a first input shaft of a transmission along the first input shaft to an output shaft of the transmission, the first input shaft being coupled to the output shaft by a plurality of shiftable gearwheel pairs and a shiftable compound gearwheel idly mounted on the first input shaft, the transmission further comprising a second input shaft parallel to the first input shaft and selectively couplable to the first input shaft via a plurality of gearwheels operable to vary the rotational speed of the second input shaft relative to the first input shaft, the second input shaft being selectively couplable to the output shaft and coaxial with the output shaft, the compound gearwheel on the first input shaft being engaged with a gearwheel on the second input shaft and engaged with a shiftable gearwheel idly mounted on the output shaft, the transmission further comprising a first reversible drive machine coupled to the second input shaft and a second reversible drive machine coupled to the first input shaft, the transmission further comprising an energy storage system electrically connected with the second reversible drive machine;
• transmitting torque provided by the first reversible drive machine to the output shaft;
• decreasing the torque provided to the output shaft by the irreversible drive machine;
• increasing the torque provided to the output shaft by the first reversible drive machine;
• changing a gear ratio by which the irreversible drive machine transmits torque to the output shaft;
• and
• increasing the torque provided to the output shaft by the irreversible drive machine, wherein the total torque provided to the output shaft before, during, and after changing of the gear ratio is substantially constant.

A hybrid drive system for a vehicle, comprising:

• a transmission having a first input shaft coupled to an output shaft and coupled to a second input shaft, the output shaft and the second input shaft being coaxial, the first input shaft and the output shaft being coupled by a plurality of shiftable gearwheel pairs and a shiftable compound gearwheel, the compound gearwheel being idly mounted on the first input shaft and engaged with a gearwheel on the second input shaft and engaged with a shiftable gearwheel idly mounted on the output shaft;
• at least one irreversible drive machine coupled to the first input shaft;
• a first reversible drive machine coupled to the second input shaft, the second input shaft being selectively couplable to the first input shaft and selectively couplable to the output shaft;
• and
• a second reversible drive machine coupled to the first input shaft.