Patent Application
20080111385
This application is based on and claims priority under 35 U.S.C. ยง 119 to Japanese Patent Application 2006-305736, filed on Nov. 10, 2006, the entire content of which is incorporated herein by reference.
This invention generally relates to a method for manufacturing an impact absorber for a vehicle.
Among related manufacturing methods for impact absorbers for vehicles, for example, a method described in JP2846983B is known. According to the manufacturing method described in JP2846983B, a bumper reinforcement serving as an impact absorber is manufactured by rolling and forming a high tensile steel plate having 450 MPa or higher tensile strength and less than 2.54 mm of thickness so that the formed body has a constant cross sectional configuration in a longitudinal direction thereof, and then by bending the formed body so that the body is formed in an arc-shape (sweep forming) with a constant curvature radius in the longitudinal direction thereof (in a direction perpendicular to the cross section of the body). Here, the bumper reinforcement (the formed body) shown in cross-section includes indentations on a front wall and a rear wall respectively. The JP2846983B also discloses that the indentations serve as a roller engaging portion which is configured to engage with a roller for advancing the formed body forward during bending and forming of the formed body.
From viewpoints of formability and cost, a limit tensile strength of the high tensile steel plate that undergoes a roll forming process is about 980 MPa. In JP2846983B, the high tensile steel plate needs to be thick to satisfy strength required for the bumper reinforcement, which increases thickness of the bumper reinforcement 1, thus causing weight increment thereof.
A need thus exists for a method for manufacturing an impact absorber for a vehicle, which is not susceptible to the drawback mentioned above.
In light of the foregoing, a method for manufacturing an impact absorber for a vehicle includes a first process for manufacturing a formed body having a constant cross-sectional configuration by performing roll forming on a metal sheet and a second process for manufacturing the impact absorber by performing an induction hardening treatment and a bend forming on the formed body after performing the first process.
As shown in
A height of the front wall 11 is set to be larger than a combined height of the rear walls 12, 13. The bumper reinforcement 1 includes a connecting wall 18 interposed between the upper wall 15 and the lower wall 16, the connecting wall 18 connecting the upper wall 15 and the lower wall 16, and contacting the front wall 11. The upper wall 15, the lower wall 16 and the connecting wall 18 thereby form a recess portion S opening rearward and having a U-shaped cross section. The bumper reinforcement 1 is formed in a manner that both ends of a piece of metal sheet are joined at the center of the front wall 11 contacting the connecting wall 18, the front wall 11 welded to the connecting wall 18. Thus, a cross section of the bumper reinforcement 1 is a continuous line.
An upper enclosed region formed by the front wall 11, the rear wall 12, and the upper walls 14 and 15 has a square cross section. Similarly, a lower enclosed region formed by the front wall 11, the rear wall 13, and the lower walls 16 and 17 has a square cross section. The vertically arranged square enclosed regions are separated from each other in vertical direction by a height of the connecting wall 18.
As shown in
A method for manufacturing the bumper reinforcement 1 will be described herebelow.
The piercing machine 22 make holes on the metal sheet 2 fed out from the uncoiler 21, which correspond to the mounting holes 1c, 1c. The roll forming machine 24 includes a plurality of roller units 31 each having a pair of rollers 31a and 31b arranged vertically to each other, the roller units 31 aligned horizontally. As shown in
The laser welder 25 includes a welding nozzle 32 that emits laser light upward, with which the matched ends 2a, 2b of the formed body 3 fed out from the roll forming machine 24 are butt-welded to the formed portion 2d. Accordingly, the formed body 3 is provided with a closed cross section.
The induction hardening and bend forming machine 26 includes a high frequency ring 41, and three bending rollers 42, 43 and 44 that are movable in three directions. On the induction hardening and bend forming machine 26, the formed body 3 fed out from the laser welding machine 25 is performed with an induction hardening treatment by a high frequency wave emitted by the high frequency ring 41 (a hardening process D1). Then, the formed body 3 is moved forward between the bending rollers 42, 44 and the bending roller 43, and thus the formed body 3 is bent at portions where the hardening is performed in the hardening process, more particularly, at portions corresponding to the bent portions la, la (a bending process D2) (refer to
The cutter 27 cuts off the formed body 3, fed out from the induction hardening and bend forming machine 26, with a blade 45 into an individual bumper reinforcement 1 having a predetermined length in the longitudinal direction thereof.
Manufacturing processes for making the bumper reinforcement 1 from the metal sheet 2 are thereby completed. In sum, the plurality of bumper reinforcements 1 are continuously manufactured by advancing the metal sheet 2 wound on the uncoiler 21 through the manufacturing apparatus 20.
Next, a function of the bumper reinforcement 1 bent at the two portions will be described based on
According to the present embodiment, advantages stated below are obtained.
(1) According to the present embodiment, the metal sheet 2 with a relatively low strength, for example a tensile strength of 400 MPa, is simply roll-formed into the formed body 3 in the rolling process B. After that, the formed body 3 is made into the bumper reinforcement 1 by undergoing the induction hardening treatment in the induction hardening and bending process D, thus increasing tensile strength of the bumper reinforcement 1 up to around 1500 MPa. Consequently, the bumper reinforcement 1 satisfying a required strength and having less thickness, i.e. less weight, is manufactured. Meanwhile, restrictions posed on the tensile strength (formability) relating to roll forming is alleviated. In the induction hardening and bending process D, the formed body 3 is heated and softened so as to be smoothly bent and formed in the longitudinal direction thereof.
(2) According to the present embodiment, the bumper reinforcement 1 includes the straight portion 1b located at the center thereof and extending linearly in the longitudinal direction thereof. Consequently, when a load is applied to the bumper reinforcement 1 (the straight portion 1b) in a thickness direction of the bumper reinforcement 1 (i.e. from a forward direction of the vehicle), the load is evenly distributed on the straight portion 1b, thereby restraining the bumper reinforcement 1 from being bent into two portions at one point where the load is concentrated (bent in an approximately V-shape). And thus the impact absorber for the vehicle, which satisfies the required strength is manufactured with less thickness, i.e. less weight.
(3) According to the present embodiment, the formed body 3 (the bumper reinforcement 1) includes the vertically arranged two constant square cross sectional configurations in the longitudinal direction thereof, which is ideal to efficiently increase a geometrical moment of inertia and a section modulus with reference to a center of gravity of the cross sectional configuration, i.e. section strength. The bumper reinforcement 1 is thereby manufactured to have less thickness, i.e. less weight, while satisfying the required strength. In other words, the bumper reinforcement 1 has improved section strength compared to that of the bumper reinforcement 91 according to the prior art where the constant cross sectional configuration is formed by oblique walls made by chamfering the indentations and corners.
Further, the formed body 3 (the bumper reinforcement 1) includes the vertically arranged two constant square cross sectional configurations in the longitudinal direction thereof, which causes less deformation compared to a larger cross section, thereby preventing local deformation.
(4) According to the present embodiment, the induction hardening and bending process D enables the formed body 3 to be bent and formed in multiple degrees of freedom by using the three bending rollers 42, 43 and 44 that are movable in three directions, and thus increasing flexibility in designing and enhancing support for aesthetic design.
The above described embodiment may be modified as follows:
The cross sectional configuration of the formed body 3 (the bumper reinforcement 1) formed in the rolling process B is an example. The formed body 3 does not have to include either the constant square cross sectional configuration in the longitudinal direction or a closed cross sectional configuration.
In the induction hardening and bending process D, the formed body 3 may be bent and formed to be a bumper reinforcement having a constant curvature radius in the longitudinal direction thereof or to be a bumper reinforcement bent at four portions.
The bumper reinforcement 1 may be adapted for a bumper device for a vehicle, which is mounted to a back of the vehicle. The impact absorber for the vehicle may be a reinforcing member for a vehicle door mounted to a side of the vehicle (so called a door beam).
The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-305736 | Nov 2006 | JP | national |
