Patent ID: 7614695

Claim:
A seat back structure comprising: a back frame being formed into a frame-like skeleton of a seat, the back frame comprising a connecting rod stretched in an upper portion of the seat frame and a regulating portion in a lower portion of the seat frame; and a flexible sheet-like member being provided within the back frame so as to support a passenger, the flexible sheet-like member comprising a first supporting portion, which is a back support portion, and a second supporting portion, which is a lumbar support portion, the first supporting portion being in the form of substantially U-shaped hook portions extending upward above the connecting rod portion and configured to permit downward movement and engagement with the connecting rod portion when a load of a passenger is applied to the flexible sheet-like member, the second supporting portion being engaged with the regulating portion of the back frame to regulate a substantial backward movement of the second supporting portion over a predetermined distance.