Seat adjustment device, and vehicle seat device with the seat adjustment device

A seat adjustment device for adjusting a pivot angle between a first seat member and a second seat member coupled by a hinge shaft in a relatively pivotal manner, the seat adjustment device comprising:

• a rotation adjustment mechanism including a fixed portion, which is fixed to the first seat member, and a pivot portion, which has an axis parallel to an axis of the hinge shaft and which is pivotally coupled to the fixed portion, wherein the rotation adjustment mechanism adjusts a rotation angle between the fixed portion and the pivot portion;
• an arm portion arranged on the pivot portion, wherein the arm portion outwardly extends in a radial direction from the axis of the pivot portion;
• and
• a coupling mechanism arranged between the second seat member and the arm portion, wherein the coupling mechanism moves in cooperation with rotation of the pivot portion relative to the fixed portion and relatively pivots the first seat member and the second seat member to absorb a change in an eccentric amount of the axis of the pivot portion relative to the axis of the hinge shaft, wherein
• the hinge shaft couples the first seat member and the second seat member at a first coupling point, and the arm portion and the coupling mechanism are coupled to each other at a second coupling point,
• when a first load is applied to a distal end of one of the first seat member and the second seat member, a moment acts on the first coupling point, and a second load is applied to the second coupling point from the other one of the first seat member and the second seat member based on the moment, and
• a position of an axis of each of the first coupling point, the second coupling point, and the pivot portion is set so that a distance from the second coupling point to the axis of the pivot portion is shorter than a distance from the first coupling point to the second coupling point, each distance being in a direction perpendicular to an acting line of the second load applied to the second coupling point.