Power output device, hybrid vehicle, and method of controlling them

A hybrid vehicle that has at least an engine and two motors mounted thereon and is driven while causing power to be output from a drive shaft, said hybrid vehicle comprising:

• changeover means that changes over a connection state of the engine and the two motors between a parallel connection mode, in which at least part of output of the engine is transmitted in the form of mechanical power to the drive shaft and at least one of the two motors is utilized as a power source, and a series connection mode, in which at least one of the two motors converts the output of the engine into electric power and the other motor reconverts the electric power into mechanical power and outputs the mechanical power to the drive shaft, wherein one of the two motors functions as a power regulation unit, which has at least two rotating shafts and is capable of regulating magnitude of power transmitted between the at least two rotating shafts through transmission of electric power,
• said power regulation unit and the other motor are arranged in series between an output shaft of the engine and the drive shaft, and
• said changeover means comprises:
• a connection mechanism that connects and disconnects the power regulation unit with and from the other motor;
• and
• a constraint mechanism that constrains one of the at least two rotating shafts in said power regulation unit and thereby allows conversion between electric power and mechanical power in said power regulation unit in a released position of the connection mechanism, said hybrid vehicle further comprising:
• resonance detection means that detects occurrence of a resonance on at least one of the output shaft of the engine and the drive shaft;
• and
• resonance suppression control means that, when the occurrence of the resonance is detected at any shaft, controls both the connection mechanism and the constraint mechanism to restrict a torque applied on the shaft with the resonance.

A method of controlling a hybrid vehicle, said hybrid vehicle comprising:

• at least an engine and a motor as power source for causing power to be output from a drive shaft;
• and changeover means that changes over a connection state of the engine and the motor between a parallel connection mode, which transmits at least part of output of the engine to the drive shaft in the form of mechanical power, and a series connection mode, which converts the output of the engine into electric power and outputs the electric power to the drive shaft,
• said method comprising the steps of:
• (a) detecting whether or not a current gearshift position is at the reverse position;
• and
• (b) controlling said changeover means to change over the connection state to the series connection mode each and every time that it is determined that the current gearshift position is at the reverse position.