Impack absorbing member for vehicle

Abstract

The present invention relates to an impact absorbing member (14L, 14R) for vehicle which has a hollow cylindrical shape and is disposed in a vehicle between a side member (12L, 12R) and a bumper beam (10), and which is axially crushed along an axis of the impact absorbing member by receiving a compressive force into a bellows shape to absorb an impact energy upon deformation, wherein (a) the impact absorbing member includes a main body (20; 80; 90) of a hollow cylindrical shape, and a pair of attaching plates (54, 56) to which both axial ends of the main body are fixedly welded respectively; (b) the main body has, at least one axial end thereof, a flange (68, 70) protruding at least axially and being integrally formed with the main body; (c) the attaching plate has an adhered supporting portion (76) formed in parallel to the flange to be surface contacted therewith; and (d) the main body is fixedly welded to the attaching plate with the flange being surface contacted with the adhered supporting portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a set of views explaining the impact absorbing member for vehicle according to one embodiment of the present invention, in which FIG. 1A is a perspective view with this side attaching plate being omitted, and FIG. 1B is a sectional view taken along a line 1B-1B in FIG. 1A.

FIG. 2 is a sectional view of the main body of embodiment shown in FIG. 1 perpendicular to the axis thereof, and also shows a positional relation between the main body and the swell portion of the attaching plate.

FIG. 3 is a perspective view showing one attaching plate in the embodiment shown in FIG. 1.

FIG. 4 is a set of graphs showing tested results for examining the impact energy absorbing ability of plural kinds of the impact absorbing members for vehicle which are different in the inclined angle in FIG. 1, in which FIG. 4A shows a relation between the load and the displacement amount, and FIG. 4B shows a relation between the EA (energy absorption) amount and the displacement amount.

FIG. 5 is a set of views showing another embodiments in which a structure and a sectional view of the main body are modified.

FIG. 6 shows a set of view showing the impact absorbing member for vehicle, in which FIG. 6A is a schematic plan view showing one example of concrete disposing manner, and FIG. 6B is a sectional view taken along a 6B-6B line in FIG. 6A, and FIG. 6C is a view showing the crushed state of the crush box by the compressive load F.

FIG. 7 is a set of views explaining three kinds of modes for fixedly welding the main body of the impact absorbing member for vehicle in FIG. 6 to the attaching member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, an embodiment of the present invention will be explained in detail with reference to attached drawings.

A crush box 50 shown in FIG. 1 is disposed between the side member 12R and the bumper beam 10 to be used instead of the crush box 14R shown in FIG. 6, and corresponds to the claimed impact absorbing member for vehicle. This crush box 50 includes a main body 52 of hollow cylindrical shape and a pair of attaching plates 54, 56 fixedly welded respectively to both axial ends of the main body 52 integrally. The crush box 50 is disposed between the side member 12R and the bumper beam 10 in a posture where an axis of the main body 52 is substantially parallel to a front-and-rear direction of the vehicle, and fixed integrally to the side member 12R and the bumper beam 10 via attaching plates 54, 56 by bolts and the like (not shown).

The crush box 50, when receiving the compressive load from the vehicle front side resulting from the impact, crushes axially into the bellows shape in the same manner as the above-mentioned crush box 14R shown in FIG. 6C. During the deformation, the crush box 50 absorbs the impact energy to buffer the impact applied to structural members such as the side member 12R and the like of the vehicle.

FIG. 1A is a perspective view of the main body 52, and FIG. 1B is a sectional view taken along a line 1B-1B in FIG. 1A, that is the sectional view showing a fixedly welded portion between the main body 52 and the attaching plate 56. FIG. 2 is a sectional view in which the main body 52 is cut at an axially intermediate portion thereof perpendicular to the axis thereof and views the attaching plate 56. FIG. 3 is a perspective view of the attaching plate 56 viewed from a side where the main body 52 is attached thereto.

The main body 52 of a predetermined shape is molded by subjecting for example a hollow cylindrical pipe member (carbon steel tube) to a hydraulic forming. In this embodiment, as apparent from FIG. 2, a basic shape defined by a section perpendicular to the axis of the hollow cylindrical shape has a flat octagonal shape (a shape in which four corners of a rectangle are chamfered). Also, on a pair of side walls 60, 62 constructing two long sides (right-and-left sides in FIG. 2) substantially parallel to a direction of a long axis A, that is the direction of a plane including the axis C (up-and-down direction in FIG. 2) of the sectional view, at an axially intermediate portion, a pair of concave grooves 64, 66 are formed to be concaved inwardly of the hollow cylindrical shape symmetrical with respect to the axis. As a result, the main body 52 has as a whole a sectional shape of figure “8” or gourd.

In the hydraulic forming, a hydraulic pressure is applied to an inside of the pipe member for example to plastically deform it outwardly. Thus, the pipe member is fitted to a female mold to be deformed into the predetermined sectional shape. Here, a compressive force or a tensile force is axially applied to the main body upon the hydraulic forming, if needed. The main body 52 thus molded has thickness of about 1.2 mm which is thinner than 1.4 mm. Formation of the concave grooves 64, 66 over a full length of the main body 52 in the axial direction increases rigidity thereof, so that desired impact energy absorbing ability can be obtained and the weight is lightened, with the thin thickness of 1.2 mm. Here, the up-and-down direction in FIG. 2 corresponds to an up-and-down direction in a state where the main body 52 is mounted onto the vehicle.

At both axial end of the main body 52, flanges 68, 70 each protruding axially are provided integrally therewith. Hereinafter, the flange 70 protruding at the side of the attaching plate 56 will be explained in detail. As apparent from FIG. 2, the flange 70 is provided around the main body 52 except areas corresponding to the concave grooves 64, 66. Also, as shown in FIG. 1B, relative to the direction of axis of the main body 52 (up-and-down direction in FIG. 1B), the flange 70 protrudes outwardly of the hollow cylindrical shape to make an incline angle α ranging from zero to sixty degrees (0°≦α<60°). FIG. 1 and FIG. 2 show the case where the incline angle α has a positive value, and the flange 70 in inclined outwardly from the hollow cylindrical shape.

On the other hand, the attaching plate 56 is provided with a swell portion 74 at a predetermined position. That is, the swell portion 74 is formed by subjecting a part of the attaching plate 56 to be positioned inside of the hollow cylindrical shape of the main body 52 to the drawing. More specifically, the part of the attaching plate 56 to be positioned inside of the flat octagonal shape which is the basic sectional shape of the main body 52 is swelled by the drawing toward the main body 52 to form the swell portion 74. The swell portion 74 has a protruded flat surface of a trapezoidal shape, and an incline angle α of the outer peripheral wall 76 is selected to be 0°≦α<60°, so that the outer peripheral wall 76 is parallel to the above-mentioned flange 70. As a result, the flange 70 is surface contacted with the outer peripheral wall 76.

With the flange 70 being surface contacted with the outer peripheral wall 76 of the swell portion 74, the fillet-welding 78 is performed by the arc-welding along the top periphery of the flange 70, thereby being fixedly welded to the attaching plate 56 integrally. Here, the outer peripheral wall 76 functions as the claimed adhered supporting portion.

Incidentally, other flange 68 is constructed in the same manner as the flange 70. That is, the flange 68 protrudes outwardly from the hollow cylindrical shape relative to the axial direction of the main body 52 to make the incline angle α to be 0°≦α<60°. An attaching plate 54 is provided with a swell portion which has the same structure as the swell portion 74. With the flange 68 being surface contacted with an outer peripheral wall (adhered supporting portion) of the swell portion, the fillet-welding is performed by the arc-welding along a top periphery thereof. Thus, the flange 68 is fixedly welded to the swell portion 74 of the attaching plate 54 integrally.

In the crush box 50 thus constructed, the main body 52 of hollow cylindrical shape is provided with the flanges 68, 70 respectively formed at both axial ends of the main body 52 to protrude axially. These flanges 68, 70 are surface contacted with the outer peripheral walls 76 of the swell portions 74 respectively formed on the attaching plates 54, 56.

As a result, compared with the case shown in FIG. 7C in which the axial end of the main body 20 is butted to the attaching plate 22 at the right angle to be welded, the flanges 68, 70 can be suitably arc-welded to the attaching plates 54, 56 even when thickness of the main body 52 is thin. In addition, due to unnecessity or omission of the bracket, the crush box 54 rendering the desired impact energy absorbing ability can be obtained in light-weight and in low-price.

Since the main body 52 of thin thickness can be fixedly welded to the attaching plates 54, 56 suitably, by contriving the sectional shape thereof as shown in FIG. 2, thickness can be made thinner than 1.4 mm with maintaining the desired impact energy absorbing ability. In this way, weight of the main body 52 is further lightened.

In addition, when thickness of the main body 52 is made thin for the purpose of absorbing impact energy under the low load, for example to decrease damage of the vehicle upon impact in the low speed, thickness of the main body 52 can be made thinner below 1.4 mm. In this way, the main body 52 crushes even with the low load to render the impact energy absorbing operation.

In this embodiment, the inclined angle α of the flanges 68, 70 protruding outwardly from the hollow cylindrical shape relative to the axial direction of the main body 52 is selected to be 0°≦α<60°. Accordingly, the desired impact energy absorbing ability can be obtained stably, different from the case shown in FIG. 7B in which the flange bent at the right angle is fixedly welded to the attaching plate and which suffers from the drawback of the main body being bend upon inputting of the load thereto.

By the fillet-welding 78 performed along the top periphery of the flanges 68, 70, the flanges 68, 70 are easily fixedly welded to the outer peripheral wall 76 of the swell portion 74 integrally. Accordingly, the fixedly welding can be performed by the arc-welding from outside of the main body 52 easily, different from the case where the overlapped portion between the flanges 68, 70 and the outer peripheral wall 76 is fixedly welded by the spot-welding.

The part of each attaching plate 54, 56 to be positioned inside of the hollow cylindrical shape of the main body 52 is swelled toward the main body 52 by the drawing, so that the outer peripheral wall 76 of the swell portion 74 forms the adhered supporting portion to which the flanges 68, 70 are fixedly welded. For this reason, compared with the case where the part of each attaching plate 54, 56 is cut and bent-up to form the adhered supporting portion, the supporting portion of high rigidity can render the excellent supporting strength.

Here, seven kinds of test pieces of crush boxes 50 each having different incline angles α of 0°, 15°, 30°, 45°, 60°, 75° and 90° are prepared. The compressive load is applied to these crush boxes 50 in a direction parallel to the axis thereof to examine the impact energy absorbing ability by a finite element method (dynamic analysis). Thus, a test result shown in FIG. 4 was obtained. FIG. 4A is a graph showing a relation between the load and the displacement, and FIG. 4B is a graph showing a relation between EA (energy absorption) amount corresponding to an integrated value of the load shown in FIG. 4A and the displacement.

In the both graphs, a long dashed double-short dashed line shows the case of the incline angle of α=0°, a long dashed and short dashed line with narrow pitch shows the case of α=15°, a thick continuous line shows the case of α=30°, a dashed line shows the case of α=45°, a dotted line with smaller pitch than the dashed line shows the case of α=60°. A thin continuous line shows the case of α=75°, and a long dashed and short dashed line with wide pitch shows the case of α=90°. Here, the main body 52 has the thickness of 1.2 mm, the axial length of 150 mm, the up-and-down dimension in FIG. 2 being 100 mm, and the right-and-left dimension in FIG. 2 being 60 mm, respectively.

As apparent from FIGS. 4A and 4B, in the cases of α=60° to 90°, as compared with other cases, the energy absorbing amount decreases in the displacement amount larger than 70 mm. This appears to be resulted from the unstable deforming behavior of the crush box 50. That is, the crush boxes 50 are not subjected to a suitable axial crush mode where the buckle into the bellows shape is repeated sequentially by a short cycle from the load inputting direction. The crush boxes 50 began to crush from the opposite side (rear end of the vehicle) and is simultaneously subject to the buckle at plural points spaced in the longitudinal direction. As a result of such the unstable crushing, the crush box 50 tends to crush with the load of reduced magnitude, and extremely tends to yield with the load inputted from an inclined direction.

Through the above tested result, it is confirmed that the stable energy absorbing ability can be obtained by formation of the flanges 68, 70 in the incline angle range of 0°≦α<60°. Also confirmed is, in the cases of the incline angle of α=0° and α=45°, the energy absorbing amount slightly decreases, when the displacement amount exceeds 80 mm. Judging from the above fact, the range of the incline angle of 5°≦α≦40° is considered preferable, and the range of 15°≦α≦30° is considered more preferable.

For obtaining the main body 52 of this embodiment, the pipe member of the hollow cylindrical shape is formed into the figure “8” shape or the gourd shape in the sectional view thereof. However, as shown in FIG. 5A, a main body 80 of hollow cylindrical shape can be constructed by a pair of half pieces 82, 84. That is, each of the paired half pieces 82, 84 is prepared by the pressing a pair of sheet plate each having the sectional shape of figure “3”, and such sectional view corresponds a shape obtained by dividing the main body 52 by a vertical plane substantially parallel to the axis thereof. The both half pieces are disposed so that open sides are faced to each other, and end portions overlapped with each other in the up-and-down direction in FIG. 5A are fixedly welded integrally. Thus, the main body of hollow cylindrical shape can be constructed by the paired half pieces.

As shown in FIG. 5B, a main body 90 having simple rectangle sectional view (in FIG. 5B, four corners are chamfered) can be adopted. Noted is that in FIGS. 5A and 5B which are the sectional view perpendicular to the axis of the hollow cylindrical shape and each of which corresponds to FIG. 2, thickness is shown by the thick continuous line, and the flange provided at the axial ends are omitted for simplification.

Heretofore, the embodiment of the present invention was explained based on the drawings. However, noted is that the above mentioned embodiment is only one example. The present invention can be also carried out in the modes which are modified or improved according to knowledge of the skilled person.

Claims

1. An impact absorbing member for vehicle which has a hollow cylindrical shape and is disposed in a vehicle between a side member and a bumper beam, and which is axially crushed along an axis of the impact absorbing member by receiving a compressive force into a bellows shape to absorb an impact energy deformation, said impact absorbing member comprising: a main body having a hollow cylindrical shape, and axial ends to which a pair of attaching plates are fixedly welded, respectively;the main body having at least at one axial end thereof, a flange protruding at least axially and being integrally formed with the main body;the attaching plate having an adhered supporting portion formed in parallel to the flange to be surface contacted therewith; andthe main body being fixedly welded to the attaching plate with the flange being surface contacted with the adhered supporting portion.

2. An impact absorbing member for vehicle according to claim 9, wherein the flange protrudes outwardly from the hollow cylindrical shape of the main body relative to the axis thereof to make an incline angle α ranging from zero to sixty degrees (0°≦α<60°).

3. An impact absorbing member for vehicle according to claim 4, wherein the flange is fixedly welded to the adhered supporting portion integrally by a fillet-weld along a top periphery of the flange.

4. An impact absorbing member for vehicle according to claim 9, wherein the attaching plate has an enlarged portion formed by subjecting a part to be positioned inside of the hollow cylindrical shape to a drawing to swell toward the main body, and an outer peripheral wall of the swell portion forms the adhered supporting portion.

5. An impact absorbing member for vehicle according to claim 1, wherein the main body has a polygonal shape more than a hexagonal shape in a sectional shape perpendicular to the axis thereof.

6. An impact absorbing member for vehicle according to claim 5, wherein the main body is constructed of a single member.

7. An impact absorbing member for vehicle according to claim 5, wherein the main body is constructed of a pair of half pieces substantially symmetrical with respect to a plane including the axis.

8. An impact absorbing member for vehicle according to claim 5, wherein the main body has a thickness less than 1.4 mm.

9. An impact absorbing member for vehicle according to claim 5, wherein the flange is provided on an entire periphery or at least cornered portion, of the main body.

10. An impact absorbing member for vehicle according to claim 9, wherein on two faced sides of the main body a pair of concave grooves concaved inwardly are formed, and the flange is provided at an area except for the concave grooves.

11. An impact absorbing member for vehicle according to claim 9, wherein the inclined angle of the flange is preferably 5°≦α<40°, and more preferably 15°≦α<30°.

12. An impact absorbing member for vehicle according to claim 4, wherein the adhered supporting portion has a polygonal shape corresponding to the polygonal shape of the flange.

13. An impact absorbing member for vehicle according to claim 3, wherein the fillet weld is an arc-weld.