The shift control of a transmission is performed on different bases
depending on whether an engine is connected so as to be passively turned,
or is disconnected. During the disengaged state, the shift control is
performed so that the power generation efficiency of a motor-generator
becomes maximized under a predetermined condition. During the engaged
state, the shift control is performed so that the turning resistance of
the engine becomes minimized under a predetermined condition. Therefore,
during running of the vehicle, a battery can be charged through the
regeneration control of the motor-generator. Even when the regeneration
control is performed while the passive turning of the engine is allowed,
good electric power generation efficiency can be achieved.
