Patent ID: 8215426

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 transmit electric power to and from each of the first motor and the second motor; a planetary gear mechanism configured to have a first element connecting with a rotating shaft of the first motor, a second element connecting with a rotating shaft of the second motor, and a third element connecting with an engine shaft of the internal combustion engine and arranged to allow mutually differential rotations of the three elements; a connecting-disconnecting device configured to attain driving source element connection and release of the driving source element connection, the driving source element connection being any one of connection of the first motor with the first element, connection of the second motor with the second element, and connection of the internal combustion engine with the third element; a speed change-transmission assembly configured to selectively connect either one or both of the rotating shaft of the first motor and the rotating shaft of the second motor to the driveshaft and transmit the output power from the first motor and the output power from the second motor to the driveshaft at preset speed ratios; a power demand setting module configured to set a power demand as a power required for the driveshaft; and a controller configured to control the first motor and the second motor so as to make one of the first motor and the second motor, specified as a main motor, preferentially output power over the other of the first motor and the second motor, specified as an auxiliary motor, and ensure output of a power equivalent to the set power demand to the driveshaft while both of the first motor and the second motor are connected to the driveshaft by means of the speed change-transmission assembly in a state that the driving source element connection is released by the connecting-disconnecting device and operation of the internal combustion engine is stopped, wherein the controller is further configured to determine, when operation of the internal combustion engine is stopped, a speed ratio of the first motor with respect to the drive shaft and a speed ratio of the second motor with respect to the drive shaft, wherein the controller is also configured to compare the determined speed ratio of the first motor with the determined speed ratio of the second motor, and wherein the controller is additionally configured to set one of the first and second motors having the larger determined speed ratio as the main motor and to set the other of the first and second motors having the smaller determined speed ratio as the auxiliary motor, the main motor preferentially outputting power over the auxiliary motor.