Patent ID: 8827362

Claim:
A seat back frame for a vehicle seat, comprising: a pair of side frames that are disposed on both sides in a seat width direction; a supporting plate that has both ends connected to a bottom section of each of the side frames; a back plate that is formed behind the supporting plate, and connects back parts of each of the pair of side frames to each other; an upper joining part that connects an upper part of the supporting plate and an upper part of the back plate; a lower joining part that connects a lower part of the supporting plate and a lower part of the back plate; and a load transmission member that is protruded from a side frame on an outer side in a vehicle width direction of the pair of the side frames to the outer side in the vehicle width direction; wherein the supporting plate is formed into a curved shape so that a vertical cross-section of the supporting plate bulges forward with respect to the back plate and so that a center part of the supporting plate curves toward a rear side of the vehicle seat in a horizontal cross-section, the supporting plate and the back plate form a closed cross-section that extends in a seat width direction, both end parts of the back plate being connected to lower edges of the pair of side frames at a rear side of the supporting plate, the side frame on the outer side in the vehicle width direction includes a side wall that has a through hole to which a base part side of the load transmission member is inserted, and a rear wall extended on an inner side in the vehicle width direction from a rear end portion of the side wall is provided, and the base part of the load transmission member passing through the through hole of the side wall is joined to a front surface of the rear wall while a side edge part on the outer side in the vehicle width direction of the back plate is joined to a rear surface of the rear wall.