Bumper reinforcement member

1. A bumper reinforcement member of a hollow section comprising a front face, a pair of upper and lower lateral faces; wherein

a small groove and a large groove concaved to back side, which have channel shaped cross section and housed in the hollow section, are provided at the front face; and

the small groove includes a pair of upper and lower lateral faces, and a groove bottom face, the large groove includes a pair of upper and lower lateral faces, and a groove bottom face, an open space is provided between the groove bottom face of the small groove and the groove bottom face of the large groove, and the pair of upper and lower lateral faces of the small groove is totally encompassed by the pair of upper and lower lateral faces of the large groove;

the bumper reinforcement member is configured by a main reinforcement member and a supplementary reinforcement member, which are made through sheet-metal processing, the supplementary reinforcement member being positioned at back side of the main reinforcement member and being attached to the main reinforcement member;

the main reinforcement member is a hollow sectional member including the front face and the pair of upper and lower lateral faces, the small groove of channel shaped cross section including the pair of upper and lower lateral faces and the groove bottom face being provided at the front face;

the supplementary reinforcement member is a member having a front face opened structure including the pair of upper and lateral faces and the groove bottom face forming the large groove of an opened channel shaped cross section, the supplementary reinforcement member being connected to the main reinforcement member through a connection between front edges of the upper and lower lateral faces of the large groove and back side of the front face of the main reinforcement member, and connected to a vehicle side through a connection between the groove bottom face of the large groove and the vehicle side; and

the main reinforcement member is connected to the vehicle side through a connection between the vehicle side and rear edges of the upper and lower lateral faces of the main reinforcement member.

2. The bumper reinforcement member according to the claim 1 , wherein a distance A, which is defined by the smallest distance between the pair of upper and lower lateral faces of the large groove and a pair of corners of the small groove connecting the upper and lower lateral faces and the groove bottom face, a depth B of the small groove, which is defined by a distance between the front face of the bumper reinforcement member and the groove bottom face of the small groove, and a depth L of the large groove, which is defined by a distance between the front face of the bumper reinforcement member and the groove bottom face of the large groove meet a following condition;

the distance A is from 0 L to 1/10 L, and the depth B is from 1/10L to ½L.

3. The bumper reinforcement member according to the claim 1 , wherein at least former part of the pair of upper and lower lateral faces of the large groove, which totally encompasses the small groove, is fowled to a pair of inclined faces, so that a distance between the inclined faces becomes narrower towards the back side.

4. The bumper reinforcement member according to the claim 3 , wherein a pair of bulged portions is formed at a pair of corners, one of the corners connects the upper lateral face of the small groove and the front face of the reinforcement member, and a rest of the corners connects the lower lateral face of the small groove and the front face of the main reinforcement member.