Bumper beam for automobile

A bumper beam includes two tubular bodies formed by tube hydroforming that extend left and right. The tubular bodies are joined to each other in a parallel state. The tubular bodies each have a rectangular vertical cross-section shape including top and bottom and front and rear sides. The tubular bodies are disposed in a line from top to bottom, and opposing surfaces thereof are joined together across the entire length in the longitudinal direction.

BACKGROUND OF THE INVENTION

The present invention relates to a bumper beam for automobile that protects an automobile from impact on collision.

One conventional bumper beam for automobile is formed by roll casting. (See patent documents 1, 2 and 3, for example.)FIG. 41shows a vertical cross-section view of a bumper beam11disclosed in patent document 1. The bumper beam11comprises a plate material curved by roll-forming, and ends12of this plate material are welded to intermediate positions of the plate material. This bumper beam11is provided with a rib15extending between a front section13and a rear section14.FIG. 42shows a vertical cross-section view of a bumper beam21disclosed in patent document 2. This bumper beam21comprises a plate material curved by roll-forming, and end sections22,22are bent and joined so as to be entwined together.FIGS. 43 and 44show vertical cross-section views of a bumper beam31disclosed in patent document 3. This bumper beam31comprises a plate material curved by roll-forming, ends32of which are inserted into a hole33opened in an intermediate position on the plate material and thus joined thereto.

Another bumper beam for automobiles used aluminum extruded materials. For example, as shown inFIG. 45, the bumper beam41has a rectangular vertical cross-section with a reinforcement member42extending across the center as a cross beam.

Another bumper beam was formed by tube hydro-forming (for example, see Patent Document 4).FIG. 46is a plan view of this bumper beam51. The bumper beam51is made from a single tubular body. The bumper beam51comprises attachment sections52,52protruding toward the body side integrally formed by tube hydro-forming.Patent document 1: Japanese Patent Application Publication H11-170934Patent document 2: Japanese Patent Application Publication 2001-260774Patent document 3: Japanese Patent Application Publication 2002-87186Patent document 4: Japanese Patent Application Publication. 2003-104140

However, the conventional roll-formed bumper beams11,21,31or bumper beam41that used extruded material, because of their manufacturing method, have a set vertical cross-section shape in the longitudinal direction, and thus have a low degree of freedom of shape. Also, because the bumper beam51made by tube hydro-forming comprises a single tubular body, in order to ensure requisite strength, the vertical cross-section shape had to be made large, and reducing size was difficult.

The present invention was conceived in order to resolve the drawbacks of conventional bumper beams, and its object is to provide a bumper beam for automobile that can be made smaller while maintaining a high degree of freedom of shape.

SUMMARY OF THE INVENTION

To achieve the objects, the bumper beam for automobile relating to the present invention has the following constitution.

The bumper beam for automobile in accordance with a first aspect of the invention comprises a plurality of tubular bodies formed by tube hydroforming that extend in the lateral direction, such tubular bodies being joined together in a state parallel to each other. Because the tubular bodies constituting the bumper beam are formed by tube hydroforming, the vertical cross-section shape can be changed in the longitudinal direction, and the line curvature of the front surface, and so forth in the plan view can be changed in the longitudinal direction, thus allowing for a high degree of freedom in terms of shape. Because the bumper beam has a plurality of tubular bodies joined together in a parallel state, the bumper beam has a plurality of loops in the vertical cross-section, which is a constitution that is advantageous in terms of strength and enables size reductions.

According to a second aspect of the invention, in the bumper beam according to the first aspect of the invention, each of the plurality of tubular bodies has a substantially rectangular vertical cross-section shape comprising top and bottom sides and front and rear sides.

According to a third aspect of the invention, in the bumper beam according to the first aspect of the invention, the plurality of tubular bodies are disposed arrayed vertically.

According to a fourth aspect of the invention, in the bumper beam according to the third aspect of the invention, the upper surface of the uppermost tubular body among the plurality of tubular bodies projects upwardly in the center section excluding the two ends in the longitudinal direction.

According to a fifth aspect of the invention, in the bumper beam according to the third aspect of the invention, the lower surface of the bottommost tubular body among the plurality of tubular bodies projects downwardly in the center section excluding the two ends in the longitudinal direction.

According to a sixth aspect of the invention, in the bumper beam according to the first aspect of the invention, the plurality of tubular bodies are disposed arrayed front to rear.

According to a seventh aspect of the invention, in the bumper beam according to the first aspect of the invention, in the plurality of tubular bodies, surfaces that face each other are joined across the entire length in the longitudinal direction.

According to an eighth aspect of the invention, in the bumper beam according to the first aspect of the invention, at least two tubular bodies among the plurality of tubular bodies have mutually different plate thicknesses.

According to a ninth aspect of the invention, in the bumper beam according to the first aspect of the invention, at least two tubular bodies among the plurality of tubular bodies are made from mutually different materials.

According to a tenth aspect of the invention, in the bumper beam according to the third aspect of the invention, two tubular bodies are provided. For the upper of these tubular bodies, the two ends in the longitudinal direction are formed horizontally, and the upper surface of the center section excluding the ends in the longitudinal direction is formed projecting upwardly. For the lower of the two tubular bodies, the ends in the longitudinal direction are formed horizontally so as to join with the upper tubular body.

According to an eleventh aspect of the invention, in the bumper beam according to the tenth aspect of the invention, the lower surface of the lower tubular body is formed horizontally across the entire length in the longitudinal direction.

According to a twelfth aspect of the invention, in the bumper beam according to the eleventh aspect of the invention, for the upper tubular body, the lower surface of the center section excluding the two ends in the longitudinal direction is formed depressed upwardly only to an extent less than the extent to which the upper surface projects upwardly, and for the lower tubular body, the upper surface of the center section excluding the two ends in the longitudinal direction is formed projecting upwardly so as to join with the lower surface of the upper tubular body.

According to a thirteenth aspect of the invention, in the bumper beam according to the eleventh aspect of the invention, for the upper tubular body, the center section excluding both ends in the longitudinal direction is curved so as to project upwardly, and for the lower tubular body, the upper surface of the center section excluding both ends in the longitudinal direction is formed projecting upwardly so as to join with the lower surface of the upper tubular body.

According to a fourteenth aspect of the invention, in the bumper beam according to the tenth aspect of the invention, the center section excluding both ends in the longitudinal direction of the upper tubular body is formed curved so as to project upwardly, and the lower tubular body is formed horizontally across the entire length in the longitudinal direction.

According to a fifteenth aspect of the invention, in the bumper beam according to the tenth aspect of the invention, for the lower tubular body, the lower surface of the center section excluding both ends in the longitudinal direction is formed so as to project downwardly.

According to a sixteenth aspect of the invention, in the bumper beam according to the fifteenth aspect of the invention, for the upper tubular body, the lower surface is formed horizontally across the entire length in the longitudinal direction, and for the lower tubular body, the upper surface is formed horizontally across the entire length in the longitudinal direction so as to join with the lower surface of the upper tubular body.

According to a seventeenth aspect of the invention, in bumper beam according to the tenth aspect of the invention, the front surface of the upper tubular body and the front surface of the lower tubular body are positioned at the same position in the front to rear direction, and the rear surface of the upper tubular body and the rear surface of the lower tubular body are positioned at the same position in the front to rear direction.

According to an eighteenth aspect of the invention, in the bumper beam according to the tenth aspect of the invention, the front surface of the upper tubular body and the front surface of the lower tubular body are positioned at the same position in the front to rear direction, and the rear surface of the upper tubular body is positioned further rearward than the rear surface of the lower tubular body.

According to a nineteenth aspect of the invention, in the bumper beam according to the tenth aspect of the invention, for the upper tubular body, a recess is formed along the longitudinal direction of the lower section of the front surface, and for the lower tubular body, a recess is formed along the longitudinal direction of the upper section of the front surface.

According to a twentieth aspect of the invention, in the bumper beam according to the tenth aspect of the invention, on the upper tubular body, a recess is formed along the longitudinal direction in the lower section of the front surface.

According to a twenty-first aspect of the invention, in the bumper beam according to the tenth aspect of the invention, on the lower tubular body, a recess is formed along the longitudinal direction in the upper section of the front surface.

According to a twenty-second aspect of the invention, in the bumper beam according to the tenth aspect of the invention, the upper tubular body has a thicker plate thickness than that of the lower tubular body.

According to a twenty-third aspect of the invention, in the bumper beam according to the sixth aspect of the invention, two tubular bodies are provided and the two tubular bodies are joined together across the entire length in the longitudinal direction.

According to a twenty-fourth aspect of the invention, in the bumper beam according to the twenty-third aspect of the invention, for the two tubular bodies, the center section excluding the two ends in the longitudinal direction is formed curved so as to project forward.

According to a twenty-fifth aspect of the invention, in the bumper beam according to the sixth aspect of the invention, two tubular bodies are provided, and the two ends in the longitudinal direction are joined to each other. Here, for the front tubular body of the two tubular bodies, the center section excluding the two ends in the longitudinal direction is formed curved so as to project forward. And for the rear tubular body of the two tubular bodies, the center section excluding the two ends in the longitudinal direction is formed curved so as to project forward only to an extent that is less than the extent to which the front tubular body projects.

In accordance with the bumper beam for automobile of the present invention, because tubular bodies formed by tube hydroforming are joined to each other in a parallel state, the bumper beam can be made small while retaining a high degree of freedom of shape.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-3show a first embodiment of the present invention. The legend1in the drawings is a bumper beam for automobile that protects an automobile from impact in a collision. This bumper beam1is a constituent body disposed on the inner side of a bumper face, and extends longitudinally left and right and is attached to the front or rear of an automobile.

This bumper beam1comprises a plurality of tubular bodies2,2formed by tube hydroforming and extending left and right. The plurality of tubular bodies2,2of the bumper beam1are joined to each other in a parallel state. Here, the vertical cross-section shape of each of the plurality of tubular bodies2,2(i.e., the cross section orthogonal to the tubular body longitudinal direction) have a substantially rectangular shape comprising the top and bottom and front and rear sides (seeFIG. 3). The surfaces of the plurality of tubular bodies2,2that face each other across the entire length in the longitudinal direction are joined to each other. More specifically, the plurality of tubular bodies2,2are disposed in a line vertically. The two ends3,3in the longitudinal direction of the uppermost tubular body2of the plurality of tubular bodies2,2are formed horizontally. Furthermore, for the uppermost tubular body2of the plurality of tubular bodies2,2, an upper surface5of a center section4excluding the two ends3,3in the longitudinal direction is formed to project upwardly.

Specifically, the bumper beam1comprises two tubular bodies2. The tubular bodies2,2are made, for example, of high-tensile steel. The two ends3,3in the longitudinal direction of the upper tubular body2of the two tubular bodies2,2are formed horizontally. For the upper tubular body2, the upper surface5of the center section4excluding the two ends3,3in the longitudinal direction is formed to project upwardly. Meanwhile, for the lower tubular body2of the two tubular bodies2,2, the two ends3,3in the longitudinal direction are formed horizontally so as to join with the upper tubular body2. For the lower tubular body2, a lower surface6is formed horizontally along the entire length, including the two ends3,3in the longitudinal direction.

For the upper tubular body2, the lower surface6of the center section4excluding the two ends3,3in the longitudinal direction is formed depressed upwardly to an extent that is smaller than the extent to which the upper surface5projects. For the lower tubular body2, the upper surface5of the center section4excluding the two ends3,3, in the longitudinal direction is formed to project upwardly so as to join with the lower surface6of the upper tubular body2. Thus, the tubular bodies2,2are joined together across the entire length in the longitudinal direction. More specifically, for the two tubular bodies2,2, the lower surface6of the upper tubular body2and the upper surface5of the lower tubular body2, which face each other, are joined across the entire length in the longitudinal direction.

A front surface7of the upper tubular body2and a front surface7of the lower tubular body2are positioned at the same position in the front and rear directions. Similarly, a rear surface8of the upper tubular body2and a rear surface8of the lower tubular body2are positioned at the same position in the front and rear directions. For each of the tubular bodies2,2, the two ends3,3in the longitudinal direction extend substantially directly sideways, and the center section4excluding the two ends3,3in the longitudinal direction is formed curved so as to project forward.

In the upper tubular body2, a recess9ais formed along the longitudinal direction on the lower section of the front surface, excluding the two ends3,3. In the lower tubular body2, a recess9bis formed along the longitudinal direction on the upper section of the front surface, excluding the two ends3,3. These tubular bodies2,2are joined in a parallel state, by welding, adhesion, bolting or the like.

FIGS. 4-6show a second embodiment of the present invention. This embodiment differs from the first embodiment in that in the upper tubular body2and the lower tubular body2, the positions of the joining surfaces in the center sections4,4excluding the two ends3,3in the longitudinal direction are different, and in that this embodiment does not have the recesses9aand9b, but the two embodiments are substantially the same in other respects. An explanation will be given primarily of the differences.

In the upper tubular body2in the bumper beam1, in the center section4excluding the two ends3,3in the longitudinal direction, the lower surface6is depressed upwardly to the same extent that the upper surface5projects. More specifically, the center section4of upper tubular body2excluding the two ends3,3in the longitudinal direction is formed curved so as to project upwardly. In the lower tubular body2of the bumper beam1, the upper surface5of the center section4excluding the two ends3,3in the longitudinal direction is formed projecting upwardly so as to join with the lower surface6of the upper tubular body2. Thus, for the two tubular bodies2,2, surfaces facing each other (i.e., the lower surface6of the upper tubular body2and the upper surface5of the lower tubular body2) are joined across the entire length in the longitudinal direction.

The front surface7of the upper tubular body2and the front surface7of the lower tubular body2are positioned at the same position in the front and rear directions. Similarly, the rear surface8of the upper tubular body2and the rear surface8of the lower tubular body2are positioned at the same position in the front and rear directions. The tubular bodies2,2are formed curved so as to project forward across the entire length in the longitudinal direction.

FIGS. 7-9show a third embodiment of the present invention. The third embodiment differs from the second embodiment in that in the lower tubular body2, the shape of the upper surface5of the center section4excluding the two ends3,3in the longitudinal direction is different; however, the two embodiments are substantially the same in other respects. An explanation will be given primarily of the differences.

In the upper tubular body2of the bumper beam1, the center section4excluding the two ends3,3in the longitudinal direction is curved so as to project upwardly, but the lower tubular body2is formed horizontally along the entire length in the longitudinal direction. Thus, the upper tubular body2and the lower tubular body2have center sections4,4excluding the two ends3,3in the longitudinal direction that are separated from each other. (More specifically, the lower surface6of the upper tubular body2and the upper surface5of the lower tubular body2are separated from each other.)

FIGS. 10-12show a fourth embodiment of the present invention. This embodiment differs from the second embodiment in that for the upper tubular body2, the lower surface6in the center section4excluding the two ends3,3in the longitudinal direction is shaped differently, and for the lower tubular body2, the upper surface5and the lower surface6in the center section excluding the two ends3,3in the longitudinal direction are shaped differently, but the two embodiments are substantially the same in other respects. An explanation will be given primarily of the differences.

In the upper tubular body2of the bumper beam1the lower surface6is formed horizontally along the entire length in the longitudinal direction. In the lower tubular body2in the bumper beam1, the upper surface5is formed horizontally along the entire length in the longitudinal direction so as to join with the lower surface6of the upper tubular body2. Thus, surfaces that face each other of the two tubular bodies2,2are joined across the entire length in the longitudinal direction.

In the lower tubular body2, the lower surface6of the center section4excluding the two ends3,3in the longitudinal direction is formed projecting downwardly. Generally, in cases where the bumper beam1comprises a plurality of tubular bodies2,2, including cases where it comprises two tubular bodies2,2, in the lowermost tubular body2of the plurality of tubular bodies2,2, the lower surface6is formed to project downwardly in the center section4excluding the two ends3,3in the longitudinal direction.

FIGS. 13-15show a fifth embodiment of the present invention. This embodiment differs from the first embodiment in that the upper and lower tubular bodies2,2have differently shaped center sections4excluding both ends3,3in the longitudinal direction, and in that there are no recesses9aand9b; however, the two embodiments are substantially the same in other respects. An explanation will be given primarily of the differences.

The upper tubular body2and the lower tubular body2of the bumper beam1are formed horizontally along the entire length, including the two ends3,3in the longitudinal direction. More specifically, for the upper tubular body2and the lower tubular body2, the upper surfaces5and the lower surfaces6are formed horizontally across the entire length in the longitudinal direction. And for the two tubular bodies2,2, surfaces that face each other across the entire length in the longitudinal direction (i.e., the lower surface6of the upper tubular body2and the upper surface5of the lower tubular body2) are joined. Further the two tubular bodies2,2have the same vertical cross-section shape and same plate thickness. (SeeFIG. 15).

FIG. 16shows a sixth embodiment of the present invention. This embodiment differs from the fifth embodiment in that the plate thickness of the two tubular bodies2,2is not the same. More specifically, of the two tubular bodies2,2that constitute the bumper beam1, the upper tubular body2has a plate thickness that is thicker than that of the lower tubular body2. Generally, in cases where the bumper beam1comprises a plurality of tubular bodies2,2, including cases where it comprises two tubular bodies2,2, at least two tubular bodies2,2of the plurality of tubular bodies2,2have plate thicknesses that are different from one another.

FIGS. 17-19show a seventh embodiment of the present invention. This embodiment differs from the fifth embodiment in that the vertical cross-section shapes of the upper tubular body2and the lower tubular body2are not the same; otherwise they are substantially the same in other respects. An explanation will be given primarily of the differences.

In the bumper beam1, while the vertical cross-section shape of the upper tubular body2has a rectangular shape with longer vertical sides, the vertical cross-section shape of the lower tubular body2has a rectangular shape with longer horizontal sides (seeFIG. 19). Here, the front surface7of the upper tubular body2and the front surface7of the lower tubular body2are positioned at the same position in the front and rear directions. Similarly, the rear surface8of the upper tubular body and the rear surface8of the lower tubular body are positioned at the same position in the front and rear directions. The tubular bodies2,2each are formed curved so as to project forward along the entire length in the longitudinal direction.

FIGS. 20-22show an eighth embodiment of the present invention. This embodiment differs from the fifth embodiment in that this embodiment is provided with recesses9a,9bin the upper and lower tubular bodies2,2, but the two embodiments are substantially the same in other respects. An explanation will be given primarily of the differences.

In the upper tubular body2of the bumper beam1, the recess9ais formed along the longitudinal direction across the entire length of the bottom section of the front surface. In the lower tubular body2in the bumper beam1, the recess9bis formed along the longitudinal direction across the entire length of the upper section of the front surface.

In the embodiment shown in the drawings, the upper tubular body2and the lower tubular body2have vertical cross-section shapes that are vertical inversions of each other (seeFIG. 22). Each of the tubular bodies2,2is formed curved so as to project forward across the entire length in the longitudinal direction.

FIGS. 23-25show a ninth embodiment of the present invention. This embodiment differs from the eighth embodiment in that it is provided with a recess9bonly in the lower tubular body2, but the two embodiments are substantially the same in other respects.

More specifically, in the bumper beam1, while the upper tubular body does not have the recess9a, the lower tubular body2has the recess9bformed along the longitudinal direction across the entire length on the upper section of the front surface.

FIGS. 26-28show a tenth embodiment of the present invention. This embodiment differs from the eighth embodiment in that only the upper tubular body2is provided with a recess9a, and that the plate thicknesses of the two tubular bodies2,2are not the same; however, the two embodiments are substantially the same in other respects.

More specifically, while the lower tubular body2does not have the recess9b, the upper tubular body2has the recess9bformed along the longitudinal direction across the entire length on the lower section of the front surface. Further, the plate thicknesses of the two tubular bodies2,2are different from each other. In the embodiment shown in the drawings, the plate thickness of the upper tubular body2is thicker than that of the lower tubular body2.

FIGS. 29-31show an eleventh embodiment of the present invention. This embodiment differs from the fifth embodiment in that the positions of the rear surfaces8,8of the upper tubular body2and the lower tubular body are not the same; however, in other respects the two embodiments are substantially the same. An explanation will be given primarily of the differences.

In the bumper beam1, the front surface7of the upper tubular body2and the front surface7of the lower tubular body2are positioned at the same position in the front and rear directions, but the rear surface8of the upper tubular body2is positioned further rearward than the rear surface8of the lower tubular body2(seeFIGS. 29 and 31).

In the embodiment shown in the drawings, while the vertical cross-section shape of the upper tubular body2has a rectangular shape that is long in the horizontal direction, the vertical cross-section shape of the lower tubular body2has a rectangular shape that is long in the vertical direction (seeFIG. 31). The tubular bodies2,2each are formed curved so as to project forward across the entire length in the longitudinal direction.

FIGS. 32-34show a twelfth embodiment of the present invention. This embodiment differs from the eleventh embodiment in that a recess9bis provided to the lower tubular body2, but the two embodiments are substantially the same in other respects. More specifically, in this bumper beam1, on the lower tubular body2, the recess9bis formed along the longitudinal direction extending the entire length of the upper section of the front surface.

FIGS. 35-37show a thirteenth embodiment of the present invention. This embodiment differs from the fifth embodiment in that the directions in which the tubular bodies2,2are arrayed is different, but the two embodiments are substantially the same in other respects. More specifically, a plurality of tubular bodies2,2constituting the bumper beam1(in the embodiment shown in the drawing, the two tubular bodies2,2) are disposed arrayed front to rear.

Specifically, the tubular bodies2,2each are formed horizontally across the entire length in the longitudinal direction. More specifically, in the front tubular body2and the rear tubular body2, the upper surface5and the lower surface6are formed horizontally across the entire length in the longitudinal direction. For each of the tubular bodies2,2, the two ends3,3in the longitudinal direction extend substantially directly sideways, and the center section4excluding the two ends3,3in the longitudinal direction is curved so as to project forward. The two tubular bodies2,2are joined across the entire length in the longitudinal direction. More specifically, for the two tubular bodies2,2, the rear surface8of the front tubular body2and the front surface7of the rear tubular body2, which face each other, are joined across the entire length in the longitudinal direction.

FIGS. 38-40show a fourteenth embodiment of the present invention. This embodiment differs from the thirteenth embodiment in that the two tubular bodies2,2are joined partially in the longitudinal direction, but the two embodiments are substantially the same in other respects. An explanation will be given primarily of the differences.

For the two tubular bodies2,2in the bumper beam1, the two ends3,3in the longitudinal direction are joined. In the front tubular body2, the center section4excluding the two ends3,3in the longitudinal direction is curved so as to project forward. In the rear tubular body2, the center section4excluding the two ends3,3in the longitudinal direction is formed curved so as to project forward to an extent less than the extent to which the front tubular body projects. Thus, in the front tubular body2and the rear tubular body2, the center sections4,4excluding the two ends3,3in the longitudinal direction (i.e., the rear surface8of the front tubular body2and the front surface7of the rear tubular body2) are separated from each other.

Next, the operational effects of the bumper beam1shown in embodiments 1-14 will be explained. In accordance with this bumper beam1, because the two tubular bodies2,2constituting the bumper beam1are formed by tube hydroforming, the vertical cross-section shape can be changed in the longitudinal direction, and the curvature of the line of the front surface7or the rear surface8as seen in a plan view or the curvature of the line of the upper surface5or the lower surface6as seen in a front view can be changed in the longitudinal direction, and thus there is a high degree of freedom with respect to shape. Therefore, this bumper beam1can be easily formed along the body lines of various types of automobiles, and easily made into a shape suitable for protecting such automobiles from collisions in accordance with the specifications of the various types of automobiles. Further, the bumper beam1comprises a plurality of tubular bodies2,2(in the embodiments in the drawings, the two tubular bodies2,2) joined together in a parallel state, and thus because of these tubular bodies2,2, the bumper beam1has a plurality of loops in its vertical cross-section (the embodiments in the drawings have two loops). Thus, because the bumper beam1has a plurality of loops in its vertical cross-section (two loops in the embodiments in the drawings), the constitution is advantageous in terms of strength, and the bumper beam can be made smaller (more specifically, the depth, i.e., the front-to-rear dimension, can be made smaller) and there can be leeway in terms of space on the body side of the automobile. More specifically, in accordance with the bumper beam1, by joining the tubular bodies2,2formed by tube hydroforming together in a parallel state, the bumper beam1can be made smaller while retaining a high degree of freedom with respect to shape.

Here, particularly in the embodiments other than the third and fourteenth embodiments, the tubular bodies2,2constituting the bumper beam1are joined across the entire length in the longitudinal direction. Thus, because tubular bodies2,2are joined across the entire length in the longitudinal direction, the bumper beam can be given greater rigidity.

Because plurality of tubular bodies2(in the embodiments in the drawings, two such bodies) are used, the vertical cross-section shape of these tubular bodies2,2can be changed, the plate thickness can be changed and the materials can be changed, and a vertical cross-section shape, plate thickness or materials appropriate to the disposition position of each tubular body2in the bumper beam1can be selected. In this way, a bumper beam1with nothing extraneous can be made, meaning that a lighter bumper beam1can be achieved. Regarding the vertical cross-section shape, in the seventh through twelfth embodiments, for example, the vertical cross-section shape of each of the two tubular bodies is different across the entire length in the longitudinal direction. And in the second embodiment, in the center sections4,4in the longitudinal direction, the two tubular bodies2,2have different vertical cross-section shapes. With respect to plate thickness, in the sixth and tenth embodiments, for example, the two tubular bodies2,2have different plate thicknesses. High-tensile steel is used as the material of the tubular bodies in the above embodiments, but ordinary steel, aluminum or an aluminum alloy may also be used. For example, even among high-tensile steel, materials having a tensile strength of 780 MPa or 980 MPa and so on are available, and these materials may be selected and used as appropriate. In the plurality of tubular bodies2,2constituting the bumper beam1(in the embodiments in the drawings, the two tubular bodies2,2), all of the tubular bodies2,2may be entirely made of the same materials or at least two tubular bodies from among the plurality of tubular bodies2,2may be made using different materials from each other.

In the bumper beam1shown in the third embodiment, the upper tubular body2and the lower tubular body2are separated from each other at the center sections4,4in the longitudinal direction. Thus, the vertical cross-section shape of the tubular bodies2,2can be made smaller, and a lighter bumper beam1can be achieved.

In the bumper beam1shown in the first through fourth embodiments, for the upper tubular body2, in the center section4excluding the two ends3,3in the longitudinal direction, the upper surface5is formed projecting upward, or for the lower tubular body2, in the center section4excluding the two ends3,3in the longitudinal direction, the lower surface6is formed projecting downward. In this way, because the upper surface5at the center section4of the upper tubular body2projects upward, the bumper beam1can handle an impact at an upward position, with the two ends3,3in the longitudinal direction as is. And because the lower surface6at the center section4of the lower tubular body2projects downward, the bumper beam1can handle an impact at a downward position, with the two ends3,3in the longitudinal direction as is.

As with the bumper beam1shown in the first, eighth through tenth, and twelfth embodiments, by providing the tubular body2with the recesses9a,9balong the longitudinal direction, the rigidity of the bumper beam1can be increased. And in these embodiments, the recess9ain the upper tubular body2is provided at the lower section of the front surface of the tubular body2, and the recess9bin the lower tubular body2is provided at the upper section of the front surface of the tubular body2. Therefore, because of these recesses9a,9b, height with respect to impact can be maintained, without reducing top to bottom height of the front surface7of the bumper beam1.

This invention is not limited to the embodiments described above; various other modifications may be made. For example, the bumper beam1may comprise three or more tubular bodies2,2instead of two tubular bodies2,2. Alternatively, a plurality of tubular bodies2,2constituting the bumper beam1may all be disposed arrayed vertically, or all disposed arrayed front to rear, or may be disposed lined up both vertically and from front to rear.

The vertical cross-section shape of the tubular body2may be trapezoidal or some other shape than rectangular.

The tubular bodies2,2constituting the bumper beam1is arrayed so that the ends in the longitudinal direction line up; however, the ends may be made to not line up by changing the length of the tubular body2.

The various elements in the bumper beams1shown in the embodiments described above may of course be assembled as appropriate to form a new bumper beam1. For example, the bumper beam1shown in the thirteenth and fourteenth embodiments may be made so that the front tubular body2and the rear tubular body2are made from different materials or have different plate thicknesses. Thus impact absorption efficiency of the bumper beam1in an automobile impact can be increased.