Automatic transmission, control method of automatic transmission, vehicle and control method of vehicle

A control method of an automatic transmission which comprises:

• a first transmission mechanism to which a driving force of a driving source is input through a first clutch and which is configured to switch driving force transmission paths to an output member to establish a first set of gear ratios;
• and
• a second transmission mechanism to which the driving force of the driving source is input through a second clutch and which is configured to switch driving force transmission paths to the output member to establish a second set of gear ratios,
• a one-way clutch is provided in the driving force transmission path that establishes a first certain gear ratio in the first set,
• wherein the first transmission mechanism comprises:
• an input shaft to which the driving force of the driving source is input through the first clutch;
• a first transmission gear provided on the input shaft and configured to establish the first certain gear ratio;
• a plurality of second transmission gears provided on the input shaft and configured to establish remaining gear stages in the first set;
• and
• a switching mechanism configured to perform engagement and disengagement between the input shaft and the plurality of second transmission gears, and
• a driving transmission direction of the one-way clutch is set such that a rotation inputted from a wheel side to the output member in a predetermined rotational direction is transmitted to the input shaft, the predetermined rotational direction corresponding to a backward movement of a vehicle,
• the control method comprising:
• determining whether disengagement by the switching mechanism is impossible;
• and
• upon determining that the disengagement is impossible, executing recovery control to enable the disengagement on condition that a driver performs a predetermined operation.