disengaged torque generated by the first motor generator 1 is supplied through the first sun gear reduced according to a gear ratio of the first planetary gear set 5 and then outputted to the output shaft 3 through the first carrier for illustration purposes the rotational direction of the output shaft 3 is defined as a normal direction and the opposite direction is defined as an inverse direction hereafter because the engine 7 is stopped the second motor generator 9 connected with the second sun gear is rotated in the inverse direction without torque as the second motor generator 9 that has rotated in the inverse direction in the electric vehicle mode is rotated in the normal direction as shown in fig3 the engine 7 increases in rotational velocity can be started and generate torque and thus power supplied from the first motor generator 11 and power supplied from the engine 7 are simultaneously outputted to the output shaft 5 thereby achieving a first hybrid mode in the first hybrid mode the first brake 13 is engaged while the second brake 15 and the clutch 17 are disengaged in the above operation the second motor generator 9 functions as a generator that provides a reaction force according to the torque of the engine 7 thereby substantially controlling the shift ratio the first motor generator 1 cannot control the shift ratio because the first ring gear is fixed by the first brake 13 such that it only functions as a motor that transmits torque to the output shaft 3 through the first carrier fig4 illustrates a second hybrid mode that is different.