Variable ratio power-split hybrid transmission

1. A transmission comprising:

an input member;

an output member;

a stationary member;

a first and a second planetary gear set each having a first member, a second member and a third member;

a power-split unit including the first planetary gear set and having:

a first electric motor/generator having a first rotor connected for rotation with the first member of the first planetary gear set and a first stator grounded to the stationary member;

a second electric motor/generator having a second rotor connected for rotation with the second member of the first planetary gear set and a second stator grounded to the stationary member; wherein the second member of the first planetary gear set is connected for common rotation with the output member;

a ratio-changing unit including the second planetary gear set and having:

a first torque-transmitting mechanism selectively engageable to establish torque flow between the first member of the second planetary gear set and the third member of the first planetary gear set;

a second torque-transmitting mechanism selectively engageable to establish torque flow between the second member of the second planetary gear set and the third member of the first planetary gear set; the first and second torque-transmitting mechanisms thereby providing two different speed ratios between the input member and the third member of the first planetary gear set; wherein the first member of the second planetary gear set is connected for common rotation with the input member; and wherein the third member of the second planetary gear set is grounded to the stationary member.

2. The transmission of claim 1 , wherein the transmission is operable in a first input-split operating mode when the first torque-transmitting mechanism is engaged; and wherein the transmission is operable in a second power-split operating mode when the second torque-transmitting mechanism is engaged.

3. The transmission of claim 2 , wherein the transmission is operable in a first electric-only operating mode when the second motor/generator is operated as a motor and neither of the torque-transmitting mechanisms are engaged; and wherein the transmission is operable in a second electric-only operating mode when the first and the second motor/generators are operated as motors and both of the torque-transmitting mechanisms are engaged.

4. The transmission of claim 1 , in combination with an engine; and further comprising:

a damper connected between the engine and the input member.

5. The transmission of claim 1 , wherein the first member of the first planetary gear set is a sun gear member, the second member of the first planetary gear set is a ring gear member, and the third member of the first planetary gear set is a carrier member that supports pinion gears that mesh with the sun gear member and the ring gear member.

6. The transmission of claim 1 , wherein the first member of the second planetary gear set is a carrier member, the second member of the second planetary gear set is a sun gear member, and the third member of the second planetary gear set is a ring gear member; wherein the carrier member supports pinion gears that mesh with the sun gear member and the ring gear member.

7. The transmission of claim 1 , wherein the first member of the first planetary gear set is a sun gear member, the second member of the first planetary gear set is a ring gear member, and the third member of the first planetary gear set is a carrier member that supports pinion gears that mesh with the sun gear member and the ring gear member; and

wherein the first member of the second planetary gear set is a carrier member, the second member of the second planetary gear set is a sun gear member, and the third member of the second planetary gear set is a ring gear member; wherein the carrier member supports pinion gears that mesh with the sun gear member and the ring gear member.

8. The transmission of claim 1 , further comprising:

a set of intermeshing gears connected to the output member.

9. The transmission of claim 1 , wherein each of the torque-transmitting mechanisms is engaged at respective different predetermined operating conditions selected so that speeds of the first and second rotors remain within a predetermined range of speeds.

10. The transmission of claim 1 , in combination with an engine having a rotatable engine output member connected for rotation with the input member via a damper; wherein the first and second torque-transmitting mechanisms are both disengaged to disconnect the engine from the transmission and the first and second motor/generators are operated as motors to establish at least one electric-only operating mode.

11. The transmission of claim 1 , in combination with an engine having a rotatable engine output member connected for rotation with the input member; wherein the first and second torque-transmitting mechanisms are both engaged to lock the second planetary gear set and thereby prevent rotation of the engine output member and the first and second motor/generators are operated as motors to establish an electric-only operating mode.

12. The transmission of claim 1 , in combination with an engine having a rotatable engine output member operable to provide power to the second planetary gear set;

wherein the first torque-transmitting mechanism is engaged to establish a first electrically-variable operating mode, with the engine on and the motor/generators functioning as motors or generators; and

wherein the second torque-transmitting mechanism is engaged to establish a second electrically-variable operating mode, with the engine on and the motor/generators functioning as motors or generators; the first and second electrically-variable operating modes thereby being power-split operating modes with different gear ratios established between the input member and the third member of the first planetary gear set.

13. The transmission of claim 1 , in combination with an engine having a rotatable engine output member connected for rotation with the input member; wherein one of the first and second torque-transmitting mechanisms is engaged and the first motor/generator is operated as a motor to start the engine.

14. A transmission comprising:

an input member;

an output member;

a stationary member;

a first planetary gear set and a second planetary gear set, each planetary gear set having a first member, a second member, and a third member;

a first electric motor/generator having a first rotor connected for rotation with the first member of the first planetary gear set and a first stator grounded to the stationary member;

a second electric motor/generator having a second rotor connected for rotation with the second member of the first planetary gear set and a second stator grounded to the stationary member; wherein the second member of the first planetary gear set is connected for common rotation with the output member;

wherein the first member of the second planetary gear set is connected for common rotation with the input member; wherein the third member of the second planetary gear set is grounded to the stationary member;

a first torque-transmitting mechanism selectively engageable to establish torque flow between the first member of the second planetary gear set and the third member of the first planetary gear set;

a second torque-transmitting mechanism selectively engageable to establish torque flow between the second member of the second planetary gear set and the third member of the first planetary gear set; the first and second torque-transmitting mechanisms thereby providing two different speed ratios between the input member and the third member of the first planetary gear set; and

at least one controller operable to control engagement of the torque-transmitting mechanisms and the motor/generators so that the transmission thereby establishes a first input-split electrically-variable operating mode when the first torque-transmitting mechanism is engaged, the engine is on, and the motor/generators function as motors or generators, and a second input-split electrically-variable operating mode when the second torque-transmitting mechanism is engaged, the engine is on, and the motor/generators function as motors or generators, the first and second input-split electrically-variable operating modes having different gear ratios between the input member and the first planetary gear set.

15. The transmission of claim 14 , wherein the first member of the first planetary gear set is a sun gear member, the second member of the first planetary gear set is a ring gear member, and the third member of the first planetary gear set is a carrier member that supports pinion gears that mesh with the sun gear member and the ring gear member; and

wherein the first member of the second planetary gear set is a carrier member, the second member of the second planetary gear set is a sun gear member, and the third member of the second planetary gear set is a ring gear member; wherein the carrier member supports pinion gears that mesh with the sun gear member and the ring gear member.

16. A transmission comprising:

an input member;

an output member;

a stationary member;

a first and a second planetary gear set each having a first member, a second member and a third member;

a power-split unit including the first planetary gear set and having:

a first electric motor/generator having a first rotor connected for rotation with the first member of the first planetary gear set and a first stator grounded to the stationary member;

a second electric motor/generator having a second rotor connected for rotation with the second member of the first planetary gear set and a second stator grounded to the stationary member; wherein the second member of the first planetary gear set is connected for common rotation with the output member;

a ratio-changing unit including the second planetary gear set and having:

a first torque-transmitting mechanism selectively engageable to establish torque flow between the first member of the second planetary gear set and the third member of the first planetary gear set;

a second torque-transmitting mechanism selectively engageable to establish torque flow between the second member of the second planetary gear set and the third member of the first planetary gear set; the first and second torque-transmitting mechanisms thereby providing two different speed ratios between the input member and the third member of the first planetary gear set; wherein the first member of the second planetary gear set is connected for common rotation with the input member; wherein the third member of the second planetary gear set is grounded to the stationary member;

wherein the first member of the first planetary gear set is a sun gear member, the second member of the first planetary gear set is a ring gear member, and the third member of the first planetary gear set is a carrier member that supports pinion gears that mesh with the sun gear member and the ring gear member;

wherein the first member of the second planetary gear set is a carrier member, the second member of the second planetary gear set is a sun gear member, and the third member of the second planetary gear set is a ring gear member; wherein the carrier member supports pinion gears that mesh with the sun gear member and the ring gear member; and

wherein each of the torque-transmitting mechanisms is engaged at respective different predetermined operating conditions selected so that speeds of the first and second rotors remain within a predetermined range of speeds.