Control device for automatic transmission and control method for automatic transmission

A control device for an automatic transmission installed in a vehicle, wherein the vehicle has a constant speed travel mode configured to perform transmission shift control on the automatic transmission and driving force control on a driving prime mover in order to maintain a vehicle speed at a set speed, the control device comprising:

• a determination section configured to determine whether or not the vehicle is traveling on a slope road;
• a slope adaptation control section configured to implement a first transmission shift control if determined that the vehicle is not traveling on a slope road, and implement a second transmission shift control if determined that the vehicle is traveling on a slope road, wherein:
• the first transmission shift control includes selecting a predetermined transmission shift position depending on a vehicle condition;
• and
• the second transmission shift control includes selecting, depending on the vehicle condition, a transmission shift position of a lower speed in comparison with case of determined that the vehicle is not traveling on a slope road;
• a delaying section configured to implement an upshift delay control upon switching from the second transmission shift control to the first transmission shift control, wherein the upshift delay control includes performing upshift in transmission shift position one by one at a predetermined time interval;
• and
• a setting section configured to, in case that the vehicle is traveling at the constant speed travel mode, set the time interval shorter in comparison with case that the vehicle is traveling not at the constant speed travel mode.