Patent ID: 8328272

Claim:
A lower structure of a vehicle body rear portion, comprising: a rear floor panel spreading in a horizontal direction in a rear portion of a vehicle; a spare tire housing being formed on the rear floor panel in such a manner as to be recessed downward; rear side members extending in a front and rear direction of the vehicle on respective right and left ends of the rear floor panel in a width direction of the vehicle, and being made of a plate material; a rear cross member being arranged in front of the spare tire housing, and connecting the paired right and left rear side members; and a spare tire cross member being attached to the spare tire housing, and connecting the paired right and left rear side members; wherein a rear part of each of the rear side members is formed to have a rigidity lower than a rigidity of a front part thereof, the rear part extends on the vehicle rear side from a joint part joining with the spare tire cross member, and the front part extends on the vehicle front side from the joint part which joins with the spare tire cross member; wherein the rear part of each of the rear side members is formed to have a plate thickness smaller than a plate thickness of the front part of each of the rear side members, and the front part and the rear part of each of the rear side members are connected together by tailored blank welding; wherein a bead is formed in a concave shape which is concaved upwardly on a lower surface of the joint part of each of the rear side members with the spare tire cross member, so as to induce folding deformations of the rear side members when a load is applied to the vehicle body from behind the vehicle, and the bead extends in the vehicle width direction; and wherein the bead is arranged so as to correspond to a section of the joint part in which the front part and the rear part of each of the rear side members are connected together by tailored blank welding.