Drive control device for hybrid vehicle

A drive control device for a hybrid vehicle provided with:

• a differential device which includes a first differential mechanism and a second differential mechanism and which has four rotary elements;
• and an engine, a first electric motor, a second electric motor and an output rotary member which are respectively connected to said four rotary elements, and wherein one of said four rotary elements is constituted by a rotary component of said first differential mechanism and a rotary component of said second differential mechanism which are selectively connected to each other through a clutch, and one of the rotary components of said first and second differential mechanisms which are selectively connected to each other through said clutch is selectively fixed to a stationary member through a brake, said hybrid vehicle being selectively placed in a plurality of drive modes according to respective combinations of engaged and released states of said clutch and said brake, the drive control device comprising:
• a resonance point change control portion configured to switch said clutch from a presently selected one of the engaged and released states to the other, irrespective of a presently established one of said drive modes of the hybrid vehicle, when said engine is operated in a loaded condition while a torque of said second electric motor falls within a predetermined narrow range including zero,
• wherein said first differential mechanism is provided with a first rotary element connected to said first electric motor, a second rotary element connected to said engine, and a third rotary element connected to said output rotary member, while said second differential mechanism is provided with a first rotary element connected to said second electric motor, a second rotary element, and a third rotary element, one of the second and third rotary elements of the second differential mechanism being connected to the third rotary element of said first differential mechanism,
• and wherein said clutch is configured to selectively connect the second rotary element of said first differential mechanism, and the other of the second and third rotary elements of said second differential mechanism which is not connected to the third rotary element of said first differential mechanism, to each other, while said brake is configured to selectively fix the other of the second and third rotary elements of said second differential mechanism which is not connected to the third rotary element of said first differential mechanism, to the stationary member.