Hybrid drive system with multiple drive machines

1. 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;

a second reversible drive machine coupled to the first input shaft; and

an energy storage system electrically connected with the second reversible drive machine.

2. The hybrid drive system of claim 1 , wherein the first input shaft is parallel to the output shaft and parallel to the second input shaft.

3. The hybrid drive system of claim 1 , wherein the compound gearwheel includes two bonded gearwheels, and is synchronously rotatable with the first input shaft in response to engagement with a coupling device on the first input shaft.

4. The hybrid drive system of claim 1 , further comprising a dog clutch configured to engage the second input shaft and the output shaft directly at low speed and to indirectly couple the second input shaft to the output shaft via the compound gearwheel at high speed.

5. The hybrid drive system of claim 1 , wherein the compound gearwheel is mounted at an end of the first input shaft.

6. The hybrid drive system of claim 1 , wherein the compound gearwheel is mounted at a center of the first input shaft.

7. The hybrid drive system of claim 1 , wherein:

the irreversible drive machine is coupled to the first input shaft via a main clutch.

8. The hybrid drive system of claim 7 , wherein the main clutch is a frictional clutch selected from a dry clutch, a wet clutch, or a multiple plate clutch, an electromagnetic clutch, or any combination thereof.

9. The hybrid drive system of claim 7 , wherein the irreversible drive machine is an internal combustion engine that can be started by the second reversible drive machine by engaging the main clutch.

10. The hybrid drive system of claim 1 , wherein the first and second reversible drive machines are coupled to the transmission by gearwheels, belts, or chains.

11. The hybrid drive system of claim 1 , wherein the output shaft is rotatable in a reverse direction in response to reversal of the rotation of at least one of the reversible drive machines.

12. The hybrid drive system of claim 1 , wherein the transmission is configured as an automated manual transmission.

13. The hybrid drive system of claim 1 , wherein at least one of the first reversible drive machine and the second reversible drive machine is an electric motor.

14. The hybrid drive system of claim 1 , wherein:

the output shaft comprises a first gearwheel idly mounted to the output shaft, a second gearwheel idly mounted to the output shaft, and a third gearwheel idly mounted to the output shaft; and

the first gearwheel of the output shaft engages the compound gearwheel of the first input shaft; and

the second gearwheel and the third gearwheel of the output shaft are selectively engageable with the output shaft by a dog clutch mounted to the output shaft between the second and third gearwheels.

15. 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.

16. The method of claim 15 , further comprising operating the hybrid drive system in an electric vehicle mode.

17. The method of claim 15 , where:

the hybrid drive system includes at least two torque pathways from the second input shaft to the output shaft for the first reversible drive machine; and

the hybrid drive system further comprises at least two torque pathways including shiftable gearwheel pairs between the first input shaft and the output shaft for the second reversible drive machine.

18. The method of claim 15 , further comprising operating the first reversible drive machine and the second reversible drive machine as a continuously variable transmission.

19. The method of claim 15 , further comprising operating the hybrid drive system in a series hybrid mode or in a parallel hybrid mode.

20. 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.