Abstract: To provide a technique that enables the reduction of fatigue of a vehicle occupant at low cost and without an increase in the number of parts. Without preparing a sensor in addition to a posture changing mechanism, the position of a lumbar vertebra or thoracic vertebra of each vehicle occupant is estimated by controlling the operation of the posture changing mechanism. The posture changing mechanism includes: a back side support mechanism; a first motor capable of shifting a position of the back side support mechanism with respect to a vertical direction; and a second motor capable of shifting the position of the back side support member with respect to a front-back direction.

Abstract: There is provided a technique by which posture changing can be given to an occupant while the forward shift of his/her hip portion is prevented. A seat for vehicle includes a seat cushion, and a seat back coupled to the seat cushion, and the seat back includes a posture changing mechanism having a back face supporting mechanism. There is provided a technique by which 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.

Abstract: To provide a technique that enables the reduction of fatigue of a vehicle occupant at low cost and without an increase in the number of parts. Without preparing a sensor in addition to a posture changing mechanism, the position of a lumbar vertebra or thoracic vertebra of each vehicle occupant is estimated by controlling the operation of the posture changing mechanism. The posture changing mechanism includes: a back side support mechanism; a first motor capable of shifting a position of the back side support mechanism with respect to a vertical direction; and a second motor capable of shifting the position of the back side support member with respect to a front-back direction.