Patent ID: 7478690

Claim:
A power train for a hybrid electric vehicle, comprising: an engine that generates a driving force by burning a fuel; first and second motor generators that are supplied with electrical energy to generate driving forces and supplied with kinetic energies to output as electrical energy; a battery that stores the electrical energy supplied from the first and second motor generators and supplies electrical energy required for operating the first and second motor generators; a plurality of planetary gear sets that convert the driving forces output from the engine, and the first and second motor generators to have an appropriate gear ratio according to a driving state and output the converted driving forces to a driving shaft; and a plurality of breaks that are provided in the plurality of planetary gear sets and control the output revolution on the basis of the gear ratio determined according to a driving state; wherein the plurality of planetary gear sets include a first planetary gear set directly coupled to the engine and the first and second motor generators, a second planetary gear set coupled to the first planetary gear set, and a third planetary gear set coupled to the first planetary gear set and the second planetary gear set; the first planetary gear set allows the vehicle to perform a continuously variable transmission by controlling the driving forces output from the first and the second motor generators in a driving mode as an electric vehicle; the second planetary gear set transfers the driving force of the engine through a mechanical path in a low load and high speed driving mode of hybrid driving mode, and supplements the power by using the electrical energy of the battery in a stepped transmission mode exclusive to high speed mode at a low gear ratio, and the third planetary gear set transfers the driving force of the engine through a mechanical path in a high load and low speed driving mode of hybrid driving mode, and supplements the power by using the electrical energy of the battery in a stepped transmission mode exclusive to low speed mode at a high gear ratio.