Hybrid transmission with single planetary gear set and multiple operating modes

1. A powertrain comprising:

an input member;

an output member;

a stationary member;

a first and a second electric machine;

only a single planetary gear set operatively connectable between the input member and the output member and having a first member, a second member, and a third member; wherein the first, the second, and the third members include a ring gear member, a sun gear member, and a carrier member that supports pinion gears that mesh with both the ring gear member and the sun gear member;

a first, a second, a third, and a fourth selectively engageable torque-transmitting mechanism; wherein the first torque-transmitting mechanism is selectively engageable to operatively connect the second electric machine with the output member; wherein the second torque-transmitting mechanism is selectively engageable to operatively connect the second member with the output member such that the output member rotates commonly with the second member; wherein the third torque-transmitting mechanism is selectively engageable to operatively connect the third member to the stationary member; wherein the fourth torque-transmitting mechanism is selectively engageable to operatively connect the second member to the stationary member; and

wherein selective engagement of a different one or ones of the torque-transmitting mechanisms and selective operation of one or both electric machines establishes a series operating mode, an input-split operating mode, an electric-only operating mode, and a fixed gear operating mode between the input member and the output member.

2. The powertrain of claim 1 , further comprising a gear train operatively connecting the second electric machine with the output member when the first torque-transmitting mechanism is engaged.

3. The powertrain of claim 1 , wherein the first and the fourth torque transmitting mechanisms are engaged, the first electric machine is operated as a generator, and the second electric machine is operated as a motor in the series operating mode.

4. The powertrain of claim 1 , wherein the first and the second torque transmitting mechanisms are engaged, the first electric machine is operated as a motor or as a generator, and the second electric machine is operated as a motor in the input-split operating mode.

5. The powertrain of claim 1 , wherein the first torque transmitting mechanism is engaged and the second electric machine is operated as a motor in the electric-only operating mode.

6. The powertrain of claim 1 , wherein the second torque transmitting mechanism is engaged and the first electric machine is operated as a motor in the electric-only operating mode.

7. The powertrain of claim 1 , wherein the first torque transmitting mechanism and the second torque-transmitting mechanism are engaged and both the first and the second electric machines are operated as motors in the electric-only operating mode.

8. The powertrain of claim 1 , wherein the second and the third torque-transmitting mechanisms are engaged in the fixed operating mode.

9. The powertrain of claim 1 , wherein the first, the second, and the third torque-transmitting mechanisms are engaged in the fixed operating mode and the second electric machine adds torque at the output member.

10. The powertrain of claim 1 , wherein the second torque-transmitting mechanism is engaged and the first electric machine is operated as a motor or as a generator in an electric torque converter operating mode.

11. The powertrain of claim 1 , wherein the fourth torque-transmitting mechanism is engaged and the first electric machine is operated as a generator in a neutral charging operating mode.

12. A powertrain comprising:

an input member;

an output member;

a stationary member;

a first and a second electric machine;

a gear train operatively connecting the second electric machine with the output member; wherein the gear train is configured to reduce speed from the second electric machine to the output member;

only a single planetary gear set having a first member, a second member, and a third member; wherein the first, the second, and the third members include a ring gear member, a sun gear member, and a carrier member that supports pinion gears that mesh with both the ring gear member and the sun gear member;

a first, a second, a third, and a fourth selectively engageable torque-transmitting mechanism; wherein the first torque-transmitting mechanism is selectively engageable to operatively connect the second electric machine with the output member; wherein the second torque-transmitting mechanism is selectively engageable to operatively connect the second member with the output member such that the output member rotates commonly with the second member; wherein the third torque-transmitting mechanism is selectively engageable to operatively connect the third member to the stationary member; wherein the fourth torque-transmitting mechanism is selectively engageable to operatively connect the second member to the stationary member, neither of the electric machines being continuously operatively connected with the output member;

wherein selective engagement of a different one or ones of the torque-transmitting mechanisms and selective operation of one or both electric machines establishes a series operating mode, an input-split operating mode, three electric-only operating modes, and two fixed gear operating modes between the input member and the output member.

13. The powertrain of claim 12 , wherein the second torque-transmitting mechanism is engaged and the first electric machine is operated as a motor in an electric torque converter operating mode.

14. The powertrain of claim 12 , wherein the first and the fourth torque transmitting mechanisms are engaged, the first electric machine is operated as a generator, and the second electric machine is operated as a motor in the series operating mode.

15. The powertrain of claim 12 , wherein the first and the second torque transmitting mechanisms are engaged, the first electric machine is operated as a motor or as a generator, and the second electric machine is operated as a motor in the input-split operating mode.

16. The powertrain of claim 12 , wherein the first torque transmitting mechanism is engaged and the second electric machine is operated as a motor in a first of the three electric-only operating modes;

wherein the second torque transmitting mechanism is engaged and the first electric machine is operated as a motor in a second of the three electric-only operating modes; and

wherein the first torque transmitting mechanism and the second torque-transmitting mechanism are engaged and both the first and the second electric machines are operated as motors in a third of the three electric-only operating modes.

17. The powertrain of claim 12 , wherein the second and the third torque-transmitting mechanisms are engaged in a first of the two fixed operating modes; and

wherein the first, the second, and the third torque-transmitting mechanisms are engaged in a second of the two fixed operating modes.

18. A powertrain comprising:

an engine;

a hybrid transmission having:

an input member;

an output member;

a stationary member;

a first and a second electric machine;

only a single planetary gear set having a first member, a second member, and a third member; wherein the first, the second, and the third members include a ring gear member, a sun gear member, and a carrier member that supports pinion gears that mesh with both the ring gear member and the sun gear member;

a first, a second, a third, and a fourth selectively engageable torque-transmitting mechanism; wherein the first torque-transmitting mechanism is selectively engageable to operatively connect the second electric machine with the output member; wherein the second torque-transmitting mechanism is selectively engageable to operatively connect the second member with the output member such that the output member rotates commonly with the second member; wherein the third torque-transmitting mechanism is selectively engageable to operatively connect the third member to the stationary member; wherein the fourth torque-transmitting mechanism is selectively engageable to operatively connect the second member to the stationary member;

wherein selective engagement of a different one or ones of the torque-transmitting mechanisms, selective operation of the engine, and selective operation of one or both electric machines establishes:

a series operating mode in which the first and the fourth torque transmitting mechanisms are engaged, the engine is on, the first electric machine is operated as a generator, and the second electric machine is operated as a motor;

an input-split operating mode in which the first and the second torque transmitting mechanisms are engaged, the first electric machine is operated as a motor or as a generator, and the second electric machine is operated as a motor or as a generator;

an electric-only operating mode in which the first torque transmitting mechanism is engaged, the second electric machine is operated as a motor, and the first electric machine and the engine are off; and

a fixed gear operating mode in which the second and the third torque-transmitting mechanisms are engaged, the engine is on, and the electric machines are off.

19. The powertrain of claim 18 , wherein the second torque-transmitting mechanism is engaged, the first electric machine is operated as a motor, and the engine is on in an electric torque converter operating mode.

20. The powertrain of claim 18 , wherein the engine is controlled to operate at a predetermined speed and torque; wherein the fourth torque-transmitting mechanism is engaged, the first electric machine is operated as a generator receiving power from the engine in a neutral charging operating mode.