Seat for vehicle

1 . A seat for vehicle comprising:

a seat cushion; and

a seat back coupled to the seat cushion,

wherein the seat back includes a posture changing mechanism having a back face supporting mechanism,

wherein a fatigue reduction operation using the posture changing mechanism includes:

a) moving the back face supporting mechanism set to a position of a lumbar spine portion of an occupant from a first position state to a rear direction side and setting the back face supporting mechanism to a second position state; and

b) thereafter, moving the back face supporting mechanism stepwise to a front direction side from the second position state to the first position state, the stepwise movement including movement at time intervals at a constant amount,

wherein the first position state is a reference position at a pushout amount D (=0 mm) and the second position state is a maximum position M of the pushout amount, and

wherein the posture changing mechanism includes:

a first motor capable of moving a position in an up-down direction of the back face supporting mechanism;

a second motor capable of moving a position in a front-rear direction of the back face supporting mechanism; and

a control section that controls the first motor and the second motor,

the control section can set;

a first posture changing mode in which the a) and the b) are performed in such a manner that the position in the up-down direction of the back face supporting mechanism is set by the first motor so that the back face supporting mechanism is in the position of the lumbar spine portion of the occupant and the position in the front-rear direction of the back face supporting mechanism is changed by the second motor; and

a second posture changing mode in which the position in the up-down direction of the back face supporting mechanism is set by the first motor so that the back face supporting mechanism is in a position of a thoracic spine portion of the occupant and the position in the front-rear direction of the back face supporting mechanism is changed by the second motor,

the second posture changing mode includes:

a1) moving the back face supporting mechanism from the first position state to the rear direction side and setting the back face supporting mechanism to the second position state; and

b1) after a predetermined waiting time a, moving the back face supporting mechanism from the second position state to the first position state, and

a first value calculated by a product of the operation time of the back face supporting mechanism and the operation amount of the back face supporting mechanism in the first posture changing mode and a second value calculated by a product of the predetermined waiting time of the back face supporting mechanism and the operation amount of the back face supporting mechanism in the second posture changing mode are the same value.

2 . The seat for vehicle according to claim 1 , wherein a distance between the first position state and the second position state is 10 mm to 25 mm.

3 . The seat for vehicle according to claim 2 , further comprising c) repeatedly executing the a) and the b).

4 . The seat for vehicle according to claim 3 , wherein in the b), the back face supporting mechanism is moved stepwise to the front direction side at constant time intervals by a constant amount from the second position state to the first position state.

5 . The seat for vehicle according to claim 4 , wherein the constant amount is 2 mm to 5 mm.

6 . The seat for vehicle according to claim 5 , wherein the constant time is 1 minute to 2 minutes.

7 . The seat for vehicle according to claim 6 , wherein operation time of the back face supporting mechanism in the a) and the b) is 10 minutes or less.

8 . The seat for vehicle according to claim 1 , wherein, in a), the back face supporting mechanism is moved from the first position state to the second position state without stopping.