Patent ID: 8047314

Claim:
A power output apparatus configured to output power to a driveshaft, the power output apparatus comprising: an internal combustion engine; a first motor constructed to input and output power; a second motor constructed to input and output power; an accumulator arranged to supply and receive electric power from each of the first motor and the second motor; a power distribution integration mechanism configured to have a first element connected to a rotating shaft of the first motor, a second element connected to a rotating shaft of the second motor, and a third element connected to an engine shaft of the internal combustion engine, the power distribution integration mechanism allowing mutually differential rotations of the three elements; a speed change-transmission assembly constructed to selectively connect either the first element or the second element of the power distribution integration mechanism to the driveshaft and set a speed change state selected among multiple different speed change states, the speed change-transmission assembly configured to, when a speed ratio between the engine shaft and the driveshaft becomes a predetermined shift speed ratio in an n-th speed state where one of the first element and the second element is connected to the driveshaft, shift the speed change state from the n-th speed state to an (n+1)-th speed state where the other of the first element and the second element is connected to the driveshaft so as to set the speed ratio between the engine shaft and the driveshaft to a smaller value; a power demand setting module configured to set a power demand that is power required for the driveshaft; a required speed ratio setting module configured to set a required speed ratio based on the set power demand and a predetermined restriction, the required speed ratio being a required value of the speed ratio between the engine shaft and the driveshaft; and a speed change controller configured to, when the required speed ratio becomes equal to or less than a predetermined lower limit speed ratio that is less than the predetermined shift speed ratio during the n-th speed state of the speed change-transmission assembly, control the internal combustion engine, the first motor, the second motor, and the speed change-transmission assembly so as to ensure output of power equivalent to the set power demand to the driveshaft while performing an engine rotational speed adjustment of making a rotational speed of the engine shaft equal to a shift rotational speed corresponding to the shift speed ratio and a shift of the speed change state from the n-th speed state to the (n+1)-th speed state.