Abstract

A two-mode, compound-split, hybrid transmission having an input member for receiving power from a prime mover power source and an output member for delivering power from the transmission. The transmission utilizes four planetary gear sub sets, three torque transfer devices as well as first and second supplemental power receiving/delivery units--either electric motor/generator units or hydrostatic pump/motor units. At least one of the gear members in the first and second planetary gear sub sets are connected to the first supplemental power receiving/delivery units, and at least one of said gear members in the second, third and fourth planetary gear sub sets are continuously connected to the second supplemental power receiving/delivery units. Torque transfer devices selectively connect the carriers associated with the first, second and fourth planetary gear sub sets to each other and to the output member. Another torque transfer device selectively connects the carrier associated with the third planetary gear sub set to ground. That gear member of the third planetary gear sub set not connected to the second supplemental power receiving/delivery unit is connected to the carrier of the fourth planetary gear sub set. The third torque transfer device selectively grounds that gear member of the fourth planetary gear sub set not connected to the second supplemental power receiving/delivery unit.