Shift device

1. A shift device configured to be mounted on a vehicle, the shift device comprising:

a shift switching member that includes a plurality of valley parts corresponding to a shift position;

a positioning member that is provided to establish the shift position in a state of being fitted into any one of the plurality of valley parts of the shift switching member;

a motor including a rotor and a stator and driving the shift switching member;

a speed reduction mechanism section that rotates the shift switching member in a state in which a rotation speed transmitted from the motor is reduced;

a rotor rotational angle sensor that detects a rotational angle of the rotor; and

an output shaft rotational angle sensor that detects a rotational angle of the shift switching member, wherein

the shift device is configured to associate an output value of the output shaft rotational angle sensor and an output value of the rotor rotational angle sensor at a predetermined position of the positioning member with respect to at least one valley part of the plurality of valley parts of the shift switching member and detect the number of rotations of the motor based on the association, and

the predetermined position is a position between a valley bottom of the valley part of the shift switching member to a top portion of a peak part separating the adjacent valley parts.

2. The shift device according to claim 1 , further comprising:

a nonvolatile storage section that stores the association between the output value of the output shaft rotational angle sensor and the output value of the rotor rotational angle sensor at the predetermined position.

3. The shift device according to claim 2 , wherein

the storage section stores a map in which the output value of the output shaft rotational angle sensor and the output value of the rotor rotational angle sensor at the predetermined position are associated with each other, and

the shift device is configured to detect the number of rotations of the motor based on the map stored in the storage section.

4. The shift device according to claim 3 , wherein

in the map, the output values of the output shaft rotational angle sensor and the output values of the rotor rotational angle sensor are associated with each other at a plurality of the predetermined positions, and

the number of rotations of the motor is detected based on a linear interpolation of the association at the plurality of the predetermined positions.

5. The shift device according to claim 1 , wherein

the shift device is configured to associate the output values of the output shaft rotational angle sensor and the output values of the rotor rotational angle sensor at a plurality of the predetermined positions when the motor is rotated in a first direction and when the motor is rotated in a second direction opposite to the first direction.

6. The shift device according to claim 1 , wherein

the speed reduction mechanism section includes a driving-side member that is provided at a motor side, and a driven-side member that is provided in the shift switching member and is rotated according to rotation of the driving-side member,

a predetermined amount of a backlash is provided between the driving-side member and the driven-side member, and the driving-side member and the driven-side member are configured to be rotatable relative to each other by the predetermined amount of the back lash, and

the number of rotations of the motor is detected based on the association between the output values of the output shaft rotational angle sensor and the output values of the rotor rotational angle sensor in a state where the backlash between the driving-side member and the driven-side member is reduced.

7. The shift device according to claim 1 , wherein

the shift device is configured to correct the number of rotations of the motor detected based on the association, and the correction is made based on the rotational angle of the rotor detected by the rotor rotational angle sensor.