1. Field of the Invention
This invention relates to a bumper assembly for automotive vehicles and, more particularly, to improvements in a bumper reinforcement and the sectional configuration of the bumper assembly.
2. Description of the Prior Art
An example of a bumper assembly according to the prior art is as shown in FIGS. 14 through 16. As illustrated in FIG. 14, the bumper assembly includes a bumper reinforcement 1, an energy absorber 2 disposed on the load surface of the bumper reinforcement 1, and a bumper cover 3 covering the energy absorber 2 secured to the bumper reinforcement 1. The bumper assembly is secured, at the back face of the bumper reinforcement 1, to a side member 4 constituting part of the vehicle body. The bumper reinforcement 1 has a box-shaped configuration comprising a front wall 6 on which the load surface is formed, a rear wall 7 on which the back surface is formed, upper and lower walls 8, 9 connecting the front wall 6 and rear wall 7, and a horizontal intermediate wall 10 connecting the front wall 6 and rear wall 7.
A problem with this bumper reinforcement 1 is that when the reinforcement is flexed and deformed by a load such as an impact load, a bending moment in a direction which impedes the flexural deformation is produced at the joint between the bumper reinforcement 1 and side member 4, as shown in FIG. 16, since the reinforcement 1 and side member 4 are in a fixed state. As a result, there is the danger that local deformation will occur in the upper and lower walls 8, 9 near the vicinity where the bumper reinforcement 1 is fixed to the side member 4.
The means for connecting the reinforcement 1 and the side member will now be described.
An example of the connecting means according to the prior art is shown in FIG. 17. Specifically, a bumper stay 11 secured to the back surface of the bumper reinforcement 1 is fitted into the side member 4, which constitutes part of the vehicle body, and the bumper stay 11 is fixedly connected to the side member 4 by a bolt 12.
Another problem encountered in this bumper assembly is that when a load is applied in the direction of the arrow due to a collision or the like, as shown in FIG. 18, the bumper reinforcement 1 attempts to undergo flexural deformation, as indicated by the two-dot chain line, owing to the applied load. Since the bumper stay 11 and side member 4 are in a fixed state, a bending moment in a direction which impedes the flexural deformation is produced at the joint between the bumper stay 11 and side member 4. Consequently, there is the danger that local deformation 5 will occur where the bumper reinforcement 1 is fixed to the bumper stay 11, as illustrated in FIGS. 19 and 20.