Patent ID: 7179187

Claim:
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 grounding said first member of said first gear set; a second interconnecting member continuously connecting said second member of said first gear set with said first member of said second gear set; a third interconnecting member continuously connecting said second member of said second gear set with said first member of said third gear set; said first motor/generator being continuously connected with a member of said first, second or third gear set; said second motor/generator being continuously connected with a member of said first, second or third gear set which is different from said member continuously connected with said first motor/generator; a first torque transfer device selectively connecting a member of said first or second gear set with another member of said second or third gear set; a second torque transfer device selectively connecting a member of said first or second gear set with a member of said 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; a third torque transfer device selectively grounding a member of said first, second or third gear set; a fourth torque transfer device connected in parallel with one of said first and second motor/generators for selectively preventing 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.