To stabilize switching operation of a travel mode of a hybrid vehicle, for example, and reduce the occurrence of hunting.
A conditional range where energy utilization efficiency of a fixed speed change mode is higher than that of a continuous speed change mode is a range of a condition (A1) shown by a hatching in the figure. Such conditional range A1 is limited in not only a higher limit value low and a lower limit value hi, but also a vehicle speed (V) by vehicle speeds (V1) and (V2). The vehicle speed (V1) is 80 km/h, and the vehicle speed (V2) is 160 km/h, for example. Such vehicle speeds (V1) and (V2) are speeds that regulate a boundary where power circulation is generated. When a target transmission ratio (ref1) deviated from the conditional range (A1) is changed to a target transmission ratio (ref) of a conditional range (ref2), stable engagement in clutch mechanism can be obtained by switching the speed change mode from the continuous speed change mode to the fixed speed change mode.
Koji Yamamoto
Satoshi Nakamura