Electrically variable transmission having three interconnected planetary gear sets

1. An electrically variable transmission comprising:

an input member to receive power from an engine;

an output member;

first and second motor/generators;

first, second and third differential gear sets each having first, second and third members;

said input member being continuously connected with at least one member of said gear sets, and said output member being continuously connected with another member of said gear sets;

a first interconnecting member continuously connecting said first member of said first gear set with said first member of said second gear set;

a second interconnecting member continuously connecting said second member of said first gear set with said second member of said second gear set and with said second member of said third gear set;

said first motor/generator being continuously connected with said first interconnecting member;

said second motor/generator being continuously connected with a member of said second or third gear set;

a first torque transfer device selectively connecting a member of said first or second gear set with another member of said first or third gear set;

a second torque transfer device selectively connecting a member of said third gear set with another member of said first, second or third gear set, the pair of members connected by said second torque transfer device being different from the pair of members connected by said first torque transfer device; and

a third torque transfer device selectively grounding a member of said second or third gear set;

a fourth torque transfer device connected in parallel with one of said first and second motor/generators for selectively braking rotation thereof;

wherein said first, second, third and fourth torque transfer devices are engageable alone or in pairs to provide an electrically variable transmission with a continuously variable range of speed ratios and four fixed forward speed ratios.

2. The electrically variable transmission of claim 1 , wherein said first, second and third differential gear sets are planetary gear sets.

3. The electrically variable transmission of claim 2 , wherein carriers of each of said planetary gear sets are single-pinion carriers.

4. The electrically variable transmission of claim 2 , wherein at least one carrier of said planetary gear sets is a double-pinion carrier.

5. The electrically variable transmission of claim 1 , further comprising a fifth torque transfer device, such as a motor brake, connected in parallel with the other of said first and second motor/generators for selectively braking rotation thereof.

6. The electrically variable transmission of claim 1 , wherein said first, second, third and fourth torque transfer devices and said first and second motor/generators are operable to provide five operating modes in the electrically variable transmission, including battery reverse mode, EVT reverse mode, reverse and forward launch modes, continuously variable transmission range mode, and fixed ratio mode.

7. An electrically variable transmission comprising:

an input member to receive power from an engine;

an output member;

first and second motor/generators;

first, second and third differential gear sets each having first, second and third members;

said input member being continuously connected with at least one member of said gear sets, and said output member being continuously connected with another member of said gear sets;

a first interconnecting member continuously connecting said first member of said first gear set with said first member of said second gear set;

a second interconnecting member continuously connecting said second member of said first gear set with said second member of said second gear set and with said second member of said third gear set;

said first motor/generator being continuously connected with said first interconnecting member;

said second motor/generator being continuously connected with a member of said second or third gear set; and

first, second, third and fourth torque transfer devices for selectively interconnecting said members of said first, second or third gear sets with ground or with other members of said planetary gear sets, said first, second, third and fourth torque transfer devices being engageable alone or in pairs to provide an electrically variable transmission with a continuously variable range of speed ratios and four fixed forward speed ratios between said input member and said output member.

8. The electrically variable transmission of claim 7 , wherein said first, second and third differential gear sets are planetary gear sets, and said first torque transfer device selectively connects a member of said first or second planetary gear set with another member of said first or third planetary gear set.

9. The electrically variable transmission of claim 8 , wherein said second torque transfer device selectively connects a member of said third planetary gear set with another member of said first, second or third planetary gear set, the pair of members connected by said second torque transfer device being different from the pair of members connected by said first torque transfer device.

10. The electrically variable transmission of claim 9 , wherein said third torque transfer device selectively connects a member of said second or third planetary gear set with a stationary member (ground).

11. The electrically variable transmission of claim 10 , wherein said fourth torque transfer device is connected in parallel with one of said first and second motor/generators for selectively braking rotation thereof.

12. The electrically variable transmission of claim 11 , wherein carriers of each of said planetary gear sets are single-pinion carriers.

13. The electrically variable transmission of claim 11 , wherein at least one carrier of said planetary gear sets is a double-pinion carrier.

14. The electrically variable transmission of claim 11 , further comprising a fifth torque transfer device, such as a motor brake, connected in parallel with the other of said first and second motor/generators for selectively braking rotation thereof.

15. An electrically variable transmission comprising:

an input member to receive power from an engine;

an output member;

first and second motor/generators;

first, second and third differential gear sets each having first, second and third members;

said input member being continuously connected with at least one member of said gear sets, and said output member being continuously connected with another member of said gear sets;

a first interconnecting member continuously connecting said first member of said first gear set with said first member of said second gear set;

a second interconnecting member continuously connecting said second member of said first gear set with said second member of said second gear set and with said second member of said third gear set;

said first motor/generator being continuously connected with said first interconnecting member;

said second motor/generator being continuously connected with a member of said second or third gear set; and

first, second, third, fourth, and fifth torque transfer devices for selectively interconnecting said members of said first, second or third gear sets with a stationary member or with other members of said planetary gear sets;

wherein said first, second, third, fourth and fifth torque transfer devices are engageable singly or in combinations of two to provide an electrically variable transmission with a continuously variable range of speed ratios and four fixed forward speed ratios between said input member and said output member.