Mode transition control device for hybrid vehicle

A mode transition control device for a hybrid vehicle having an internal combustion engine configured to be mechanically coupled to a drive wheel via a first engagement clutch that is engaged by a first engagement stroke from a released position, a first electric motor configured to be mechanically coupled to the drive wheel via a third engagement clutch that is engaged by a third engagement stroke from a released position, a second electric motor that is mechanically coupled to the internal combustion engine, and a battery that is electrically coupled to the first electric motor and the second electric motor, and

• at the time of start, when a charge capacity of the battery is equal to or less than a predetermined value, the third engagement clutch is switched from a released state to an engaged state in a starting region by not having a slipping element as a starting element and the hybrid vehicle is started in a series HEV mode, in which the first electric motor is utilized as a drive source and receives electrical power generated by the second electric motor and the battery, and the mode transition control device comprising:
• a mode transition controller configured to carry out a control such that when a vehicle speed becomes a switchover vehicle speed while traveling in the series HEV mode, the first engagement clutch is switched from a released state to an engaged state, power generation by the second electric motor is stopped, and a traveling mode is caused to transition to a parallel HEV mode, in which the first electric motor and the internal combustion engine are used as the drive sources, and
• when a temperature rise of a second power generation system including the second electric motor is predicted after starting in the series HEV mode, the mode transition controller changes the switchover vehicle speed to a second switchover vehicle speed which is slower than a first switchover vehicle speed used prior to a determination of the temperature rise, and
• the second switchover vehicle speed is set to a vehicle speed value that corresponds to an internal combustion engine rotational speed at which the internal combustion engine is capable of self-sustaining operation.