Vehicular hood structure

1. A vehicular hood structure comprising:

a hood outer panel of a hood that covers an engine room to be opened and closed;

a hood inner panel of the hood being placed on a hood lower side of the hood outer panel;

a hood lock reinforcement that is placed between the hood outer panel and the hood inner panel to reinforce a hood front end portion, and that is equipped with a bottom portion and an extension portion, the bottom portion disposed on the hood inner panel and the extension portion disposed extending from a hood front-rear direction rear end of the bottom portion toward the hood outer panel side, and in the extension portion, the rigidity of a site at least on the hood outer panel side being set low as compared to the rigidity of the bottom portion;

a base plate that is disposed and overlapped only on the bottom portion of the hood lock reinforcement; and

a striker that is fixed to the base plate, that projects toward the hood lower side through a through hole formed in the hood inner panel, and to which locking parts on a vehicle body frame member locks,

wherein the hood lock reinforcement is formed by joining plural sheets whose sheet thicknesses are mutually different, and is configured such that a sheet thickness of the site at least on the hood outer panel side in the extension portion is set thin as compared to the sheet thickness of the bottom portion, and a vehicle width direction length in a hood vertical direction lower end of a low-rigidity portion of the extension portion is longer than a vehicle width direction length of the base plate, the rigidity in the low-rigidity portion of the extension portion being set low as compared to the rigidity of the bottom portion.

2. The vehicular hood structure according to claim 1 , wherein the extension portion is equipped with an overlap portion in which a thick sheet and a thin sheet overlap each other along a hood width direction, and the low-rigidity portion is formed by the thin sheet.

3. The vehicular hood structure according to claim 2 , wherein a first bend that bends in the hood outer panel direction toward the hood rear side is formed in a hood front-rear direction front end portion of the overlap portion, and the first bend is configured to serve as a bending deformation origin when an impactor contacts the hood.

4. The vehicular hood structure according to claim 3 , wherein a second bend that bends more toward the hood outer panel side than the first bend is formed in a hood front-rear direction rear end portion of the overlap portion, and the second bend is configured to serve, together with the first bend, as a bending deformation origin when an impactor contacts the hood.

5. The vehicular hood structure according to claim 2 , wherein the overlap portion is joined by spot welding.

6. The vehicular hood structure according to claim 2 , wherein a wall between the hood front-rear direction rear end of the bottom portion of the hood lock reinforcement and the overlap portion extends toward the hood outer panel side and diagonally upward in the hood rear direction.

7. The vehicular hood structure according to claim 1 , further comprising a dent reinforcement,

wherein the dent reinforcement and the hood lock reinforcement, which are placed between the hood outer panel and the hood inner panel and extend in the hood width direction, form a closed cross section when seen in a side sectional view in the hood front-rear direction, and wherein, at a junction positioned on the rear side of the hood between the dent reinforcement and the hood lock reinforcement, a clearance is disposed between the dent reinforcement and the hood outer panel.

8. The vehicular hood structure according to claim 7 , wherein the dent reinforcement and the hood lock reinforcement are set such that respective lengths of deformation portions in a case in which an impactor contacts the hood become equal.

9. The vehicular hood structure according to claim 1 , wherein the extension portion of the hood lock reinforcement is formed by joining plural sheets whose sheet thicknesses are mutually different such that a sheet thickness of the extension portion is varied.