Power output apparatus, vehicle equipped with power output apparatus, and control method of power output apparatus

1. 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.

2. The power output apparatus in accordance with claim 1 , wherein the main motor is one of the first motor and the second motor provided with larger speed ratio with respect to the driveshaft by the speed change-transmission assembly.

3. The power output apparatus in accordance with claim 1 , wherein the controller sets a target torque, which is to be output from the main motor, based on the set power demand to be not greater than at least a rated torque of the main motor, while setting a target torque, which is to be output from the auxiliary motor, based on the set power demand and the set target torque of the main motor.

4. The power output apparatus in accordance with claim 3 , wherein the controller sets the target torque, which is to be output from the main motor, to be less than the rated torque of the main motor and not less than a preset minimum output torque, which is smaller than the rated torque.

5. A motor vehicle equipped with drive wheels driven with power from a driveshaft, the motor vehicle 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.

6. A control method of a power output apparatus, the power output apparatus including: a driveshaft; an internal combustion engine; a first motor and a second motor respectively 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; and 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, the control method comprising:

controlling the speed change-transmission assembly to connect both the first motor and the second motor to the driveshaft 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;

determining, 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;

comparing the determined speed ratio of the first motor with the determined speed ratio of the second motor; and

controlling the first motor and the second motor 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 to ensure output of a power, which is equivalent to a power demand as a power required for the driveshaft, to the driveshaft,

wherein one of the first and second motors having the larger determined speed ratio is made the main motor, and the other of the first and second motors having the smaller determined speed ratio is made the auxiliary motor, the main motor preferentially outputting power over the auxiliary motor.

7. The control method of the power output apparatus in accordance with claim 6 , wherein one of the first motor and the second motor provided with larger speed ratio with respect to the driveshaft by the speed change-transmission assembly is specified as the main motor.

8. The control method of the power output apparatus in accordance with claim 6 , wherein a target torque which is to be output from the main motor is set based on the power demand to be not greater than at least a rated torque of the main motor, while setting a target torque which is to be output from the auxiliary motor is set based on the power demand and the set target torque of the main motor.

9. The control method of the power output apparatus in accordance with claim 8 , wherein the target torque which is to be output from the main motor is set to be less than the rated torque of the main motor and not less than a preset minimum output torque, which is smaller than the rated torque.