Vehicle fenders – Buffer or bumper type – Composite bumper
Reexamination Certificate
2003-02-11
2004-04-27
Pape, Joseph D. (Department: 3612)
Vehicle fenders
Buffer or bumper type
Composite bumper
Reexamination Certificate
active
06726261
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bumper reinforcement constructed for a part of a bumper of a vehicle.
2. Description of the Related Art
For protection of a vehicle body, a driver and other people in a vehicle such as a motorcar, a bumper is mounted on each of front and rear sides of a vehicle frame. The bumper comprises of a bumper reinforcement, as a strength member, supported by the vehicle frame, and a bumper cover, as a face member, contiguous with a vehicle exterior panel and covering the bumper reinforcement. An impact force F exerted on the bumper is absorbed substantially solely by the bumper reinforcement when the vehicle strikes another vehicle or other object. Possible impacts are grouped into light impacts and heavy impacts depending on the magnitude of the impact force F, and horizontal impacts and local impacts depending on the nature of the impact force F. The bumper reinforcement, which should protect the vehicle, driver and other people in the vehicle irrespective of the magnitude or nature of the impact force, has to be exchanged with a new one with increased frequency if it is intended to effectively absorb an impact force by deformation of the bumper reinforcement for every kind of impact. To this end, an improved bumper reinforcement has been proposed which is comprised of a bumper beam and a reinforcement member. The reinforcement member serves to absorb the impact force F in a light impact or a local impact while the bumper beam serves to absorb the impact force F in a heavy impact or a horizontal impact. This conventional art is exemplified by Japanese Patent Laid-Open Publication No. Hei 06-328988.
Specifically, according to the conventional bumper reinforcement, the reinforcement member deforms to absorb the impact force F at the beginning of exertion of the impact force or if the impact force F is small, and the bumper beam absorbs the impact force F with continued exertion of the impact force F or if the impact force F is large. This two-piece bumper reinforcement structure can achieve an increased degree of impact absorption performance compared to the conventional single-piece structure. Japanese Patent Laid-Open Publication No. 2001-322517 and U.S. Pat. No. 4,998,761 also disclose a similar two-piece bumper reinforcement.
In the bumper reinforcement of Japanese Patent Laid-Open Publication No. 2001-322517, a reinforcement member, which is to be mounted on a bumper beam at a forward surface remote from a vehicle frame, is provided with a substantially central portion that varies in cross-sectional shape so as to have a higher degree of rigidity with respect to a compressive load exerted in the front-to-rear direction compared to the remaining portions. This reinforcement member can easily absorb the impact force F as it has a slightly decreased strength tending to deform to a suitable extent. The bumper reinforcement of U.S. Pat. No. 4,998,761 is comprised of a bumper beam with a longitudinal rib, and a reinforcement member concealing the rib.
The ordinary conventional bumper reinforcement is comprised of a reinforcement member having a substantially convex cross section, and a bumper beam having a closed cross section (box type), as shown in
FIG. 10
of the accompanying drawings. When a large impact force F is exerted on the bumper reinforcement, first the reinforcement member plastically deforms and then the bumper beam plastically deforms under the impact force F transmitted from the reinforcement member, thereby absorbing the impact force (
FIGS. 11
or
12
). The transition of this impact absorption is illustrated in
FIG. 13
, which is a graph showing a relationship between the amount of displacement of the bumper beam at the forward surface and the load (impact force F) necessary to cause displacement by such an mount. This graph indicates that the load has a peak with respect to the amount of displacement and the displacement of the bumper beam progresses with respect to the low load decreasing from the peak. For this reduction of amount of impact absorption, the impact force F is absorbed not by continuous plastic deformation of the bumper beam, but the forward surface of the bumper beam is bent about the portion on which a local impact force F is exerted.
According to the bumper reinforcement of U.S. Pat. No. 4,998,761, in the presence of the rib on the forward surface of the bumper beam, the local bending of the bumper beam can be retarded with plastic deformation across a wide area, thus realizing an increased amount of impact absorption compared to the conventional bumper reinforcement described in the preceding paragraph. However, in many cases, the reinforcement member extends along only a part of the entire length of the bumper beam, and in such an event, the impact force F is exerted on the rib of the bumper beam at the portion devoid of the reinforcement member so that an effective load receiving area of the forward surface of the bumper beam is reduced to cause plastic deformation only with the low load. Consequently, the present inventors have conducted studies in an effort to realize an improved bumper reinforcement in which (1) local bending of the bumper beam is retarded with plastic deformation allowed in a wider area to increase the amount of impact absorption, and (2) plastic deformation of the bumper beam does not occur at the portion devoid of the reinforcement member.
SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to provide a bumper reinforcement in which (1) local bending of a bumper beam is retarded with plastic deformation allowed in a wider area to increase the amount of impact absorption, and (2) plastic deformation of the bumper beam does not occur at the portion devoid of a reinforcement member.
To attain the above-described object, according to the present invention, there is provided a bumper reinforcement for being attached to a front side or a rear side of a vehicle frame as a strength member, comprising a bumper beam to be supported on the vehicle frame, and a reinforcement member attached to the bumper beam on a forward side thereof which is upstream with respect to an impact exertion direction, wherein the reinforcement member has a concave portion of a substantially C-shaped cross section projecting in a downward direction reverse to the impact exertion direction, the bumper beam has, on the forward surface to which the reinforcement member is attached, a groove portion extending longitudinally of the reinforcement member, and bottom surface of the concave portion of the reinforcement member engages with a surface of the groove portion of the bumper beam.
The term “the impact exertion direction” is a direction in which the impact force F is exerted on the vehicle, namely, a direction from the front side of the vehicle toward the rear side of the vehicle in the front bumper, for example, of the ordinary vehicle, identical to the forward-to-backward direction of the vehicle. Accordingly, the position where the reinforcement member is attached to the bumper beam is the forward surface of the bumper beam in accordance with the forward-to-backward direction of an ordinary vehicle. However, if the impact force F is exerted on the vehicle from the upper side or lower side depending on the type of the vehicle, the position where the reinforcement member is attached to the bumper beam may be varied in accordance with the impact exertion direction. In the following illustrative examples, with the impact exertion direction being defined as a direction from the front surface of the bumper beam toward the rear surface of the bumper beam, the reinforcement member is attached to the front surface of the bumper beam.
Because the substantially concave portion of the reinforcement member projects in the impact exertion direction, it is possible to concentrate the impact force F transmitted to the bumper beam at the bottom surface of the concave portion. Because of a groove portion extending longitudinally of t
Goto Hiroshi
Shimotsu Koji
Koda & Androlia
Morrow Jason
Om Corporation
Pape Joseph D.
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