Device and method for switching range of automatic transmission

A method for switching a range of an automatic transmission, by which a detent mechanism is structured to be driven by an actuator, and engageable with a concave portion formed at a position corresponding to a transmission range to be positioned, so that the transmission range is changed, the method comprising:

• driving the detent mechanism to a limit position of a movement range of the detent mechanism, and driving the detent mechanism by a first predetermined amount so that the detent mechanism moves away from the limit position;
• setting a first position of the detent mechanism as a first target value for a position corresponding to a first transmission range, the first position of the detent mechanism being detected when the detent mechanism moves toward a valley of a first concave portion without being driven by the actuator, and stops naturally;
• and
• when setting a second target value for a position corresponding to a second transmission range which is different from the first transmission range of which the first position is completely set, setting a second position of the detent mechanism as the second target value for the position corresponding to the second transmission range, the second position of the detent mechanism being detected when the detent mechanism is driven by a second predetermined amount so as to move away from the first target value for the first transmission range, the first position of which is completely set, moves toward a valley of a second concave portion corresponding to the second transmission range without being driven by the actuator, and then stops naturally.