WO2004069595A2

WO2004069595A2 - Vehicle bumper support column

Info

Publication number: WO2004069595A2
Application number: PCT/IL2004/000090
Authority: WO
Inventors: Israel Reich; Yoel Bahalul; Oved Bachinsky; Avraham Yung; Alexander Barski; Inna Vilensky; Orly Shaul; Eliyahu Amami
Original assignee: Ortal Diecasting (1993) Ltd.
Priority date: 2003-01-30
Filing date: 2004-01-29
Publication date: 2004-08-19
Also published as: WO2004069595A3; IL154206A0

Abstract

An energy absorbing bumper column (20) of one piece die-casting with outer bumper connection element (12), inner chassis attachment element (16) and connecting column (20) therebetween.

Description

VEHICLE BUMPER SUPPORT COLUMN

Field and background of the invention

The present invention relates to damage prevention or reduction in vehicle collisions. More particularly, the invention provides an improved energy-absorbing bumper column which reduces damage to a powered vehicle and its occupants in a front or rear collision at low space.

The collision of a powered vehicle such as a car with a stationary or moving object generates high g forces which damage the vehicle and injure its passengers. A known method of preventing damage and injury in low-speed collisions and of reducing such injuries and damage in more severe collisions is to use an energy-absorbing support column between the vehicle chassis and the bumper.

Considering a numerical example, suppose a vehicle traveling at 10 km/hour collides with a solid concrete obstacle assumed to have zero flexibility. Suppose the vehicle bumper support is the only source of flexibility, the bumper retracting 12cm during the collision. Deceleration of the vehicle occurs during 0.086 seconds. From a speed of 2.78 m/sec deceleration will be 32 m/sec ² , which is less than 3.5 g, unlikely to cause injury or damage.

A support column may be for multiple use, for example if made of rubber or a spring. Much more energy can however be absorbed by destructive use of a metal column, which operates by buckling, shearing or similar permanent deformation and is replaced after a single use. The cost of such replacement is presently about $40 per unit. This is considerably lower than the cost of vehicle repairs likely to result from an equivalent collision where bumpers are solidly connected to the vehicle.

In order to fulfill its task such support column should absorb as much energy as possible in the limited operating length available, with the constraint that column stiffness is not excessive, which in itself would give rise to damaging high g forces. Modern automobile design allows only a short length of bumper travel for collision retraction, wherefore high deceleration within such short length is mandatory if vehicle damage is to be avoided in a low-speed collision. Such high deceleration can be achieved only by a high rate of energy absorption.

Energy-absorbing bumper supports are known in the prior art. An assessment of the state of the art can be made by review of recent US patents, each of which makes reference to many previous disclosures.

In US Patent no. 5,090,755 Gamweidner discloses an impact absorber having circular ribs which progressively shear away during impact. The flange is originally connected in one piece with the cylindrical body formed with the ribs. An annual groove provides a weakened zone which shears during impact. While this design undoubtedly achieves low cost, use is made only of the shear strength of the material. The energy absorption of bending the material is not utilized. Furthermore, after a first ring is sheared the same force is needed to shear any further ring. Thus the design lacks progressive resistance increase, as is available in bending deformation or in spring or rubber buffers.

Gerta discloses a bumper support structure in US Patent No. 5,732,801 which comprises a hollow cylinder flanged at each end. Cylinder wall has holes claimed to increase in crash force as each stage collapses.

An accordion-like collapse dining high-speed impact is claimed by McKeon for the swivel-mounted tower disclosed in US Patent no. 6,174,009 Bl. At low impact speed the tower is said to collapse as in parallelogram fashion.

Briick et al. propose a honeycomb matrix body as a support assembly in US Patent no. 6,460,667. A deformation element rests with at least one side against a support element on the support structure. In US Patent no. 6,474,709 Artner discloses a tapered sheet-metal box provided with various height formed ribs, intended to facilitate progressive collapse of the box in near concertina style, the deformed material remaining inside the box.

Werner et al. disclose a bumper system in US Patent No. 6,485,072 . An elastomer block faces a B-shaped sheet-metal form which deforms on impact.

An impact absorbing mechanism is seen in US Patent No. 6,494,510 B2 to Okamura et al. A pair of load transferring members are hinged at a central pin, so that an impact load is dispersed in two directions.

Presently one of the widest-used absorber supports comprises a rectangular extruded tube having a welded flange on one face. One unit costs approximately $40, the device comprising several steel and alurninium parts.

There is little information about how the various designs function in practice, as few- designs have seen production and practical collision tests. Some designs are heavy, which in view of the fact that four units are used per vehicle, is a substantial problem. Furtheimore the cost of known designs is high, considering that the part may need replacement sometimes more than once during the lifetime of a vehicle and that a straight such as head to head collision will destroy two units in each car.

Objects of the invention

It is therefore one of the objects of the present invention to obviate the disadvantages of prior art bumper supports and to provide an energy absorber which is low-cost, light-weight, and has superior crushing characteristics.

Summary of the invention

The present invention achieves the above objects by providing an energy-absorbing support column for a vehicle bumper, comprising an outer bumper connection element, an inner chassis attachment element spaced apart from said outer bumper connection element and a connecting column therebetween, said support column being a one-piece metal die casting.

In a preferred embodiment of the present invention there is provided a bumper support column wherein said metal is a magnesium alloy.

In a most preferred embodiment of the present invention there is provided a bumper support column as wherein the connecting column comprises a plurality of substantially X-like struts or similar disposed along the length of said connecting column, the struts being arranged between a pair of side-walls.

Yet further features of the invention will be described hereinafter.

An important innovation in the present invention is the choice of a magnesium alloy as the cast material. Magnesium has the highest strength to weight ratio of any commonly used metal. The result is that the weight saved, multiplied by the 4 units per vehicle, contribute significantly in reducing the weight of a car wherein it is used, contributing to improved performance. A further consideration is the excellent damping capacity of the metal. The use of the pressure diecasting process will enable the unit to be sold at about $20 per unit - half the price of existing bumper support energy absorbers.

In contradistinction to most other metals which provide little additional resistance after passing the yield point in an elongation test, magnesium alloy such as AM50 continues to show increased strength until breakage occurs at about 15% elongation. Thus a bumper support made of magnesium alloy demonstrates high and progressive crush resistance.

An independent test comparison using Finite Element Analysis (FEA) was conducted by the Tεchnion (Haifa, Israel) for comparing the design of the present invention with the design of a commonly used support. The critical buckling load of the conventional support column was determined to be 32 kN, while a model of the present invention supported 45.8 kN before buckling. The Technion report also includes stress/strain curves for AM50 magnesium as compared to two alumimum alloys, the significance of which will be discussed with reference to FIG. 3.

Short description of the Drawings

The invention will now be described further with reference to the accompanying drawings, which represent by example preferred embodiments of the invention. Structural details are shown only as far as necessary for a fundamental understanding thereof. The described examples, together with the drawings, will make apparent to those skilled in the art how further forms of the invention may be realized.

In the drawings:

FIG. 1 is a perspective view, seen from the outer end, of a preferred embodiment of the support according to the invention; FIG. 2 is a perspective view, seen from the inner end of the same embodiment; and

FIG. 3 displays test results of elongation tests of a preferred magnesium alloy compared with two aluminium alloys.

FIG. 4,5 and 6 illustrate further embodiments of the element according to the invention.

Full description of the Invention

There is seen in FIGS. 1 and 2 an energy-absorbing support column 10 for a vehicle bumper (not shown).

An outer bumper connection element 12 is shaped to suit the inner face of a bumper. Two connecting points 13 are provided for connection to said bumper. An aperture 14 is provided for passage of a towing hook connection. The shown embodiment is suitable for Audi cars. Similar configurations are used for other models or other cars.

An inner chassis attachment element 16 is spaced apart by about 15 - 25 cm from the outer bumper connection element 12. The inner element 16 also is configured in accordance with the car model for which it is intended. A plurality of fastener attachment holes 18 are provided for attachment to the vehicle chassis (not shown). The central section is a connecting column 20 which interconnects the elements 12, 16.

Preferably the connecting column 20 comprises a plurality of substantially X-like struts

22 disposed along the length of the connecting column 20. The struts 22 are arranged between a pair of side- walls 24.

With regard to the side walls 24, a substantially wave-shaped section 26 is provided on both sides which helps to initiate buckling and thus prevent the transmission of damage-producing high deceleration forces during a vehicle collision.

The support column 10 is a one-piece metal pressure die casting which includes the vehicle chassis and bumper screw attachment holes 14, 18.

The bumper support column 10 is preferably made of a magnesium alloy such as AM50 or similar.

FIG. 3 shows stress/strain graphs comparing the magnesium casting alloy AM50 to two high strength aluminium alloys. The graphs show that beyond 3% strain the magnesium is superior in providing progressive resistance to elongation, whereas the aluminium alloys either reached UTS (ultimate tensile strength) or provided no significant increased resistance beyond the yield point. The support 10 utilizes the increased resistance past the yield point of the magnesium alloy by means of the substantially X-like struts 22 seen in FIG.2 as part of the connecting column 20, the arms of the substantially X bending during compression of the column. As the characteristics of bending resistance are practically equivalent to that of tension resistance, the support 10 displays a continued progressive resistance to crashing even after the stressed portions of the support 10 have strained far beyond the material yield point.

As can be seen in Fig. 4,5 and 6, the columns illustrated are provided with struts of different embodiment, all having similar structure.

The scope of the described invention is intended to include all embodiments coming within the meaning of the following claims. The foregoing example illustrate a useful form of the invention, but is not to be considered as limiting its scope, as those skilled in the art will readily be aware that additional variants and modifications of the invention can be formulated without departing from the meaning of the following claims such as the use of aluminum alloy instead of a magnesium alloy or the change of the column structure.

Claims

WE CLAIM:

1. An energy-absorbing support column for a vehicle bumper, comprising an outer bumper connection element, an inner chassis attachment element spaced apart from said outer bumper connection element and a connecting column therebetween, said support column being a one-piece metal die casting.

2. The bumper support column as claimed in claim 1, wherein said metal is a magnesium alloy.

3. The bumper support column as claimed in claim 1, wherein said metal is a aluminum alloy.

4. The bumper support column as claimed in claim 1, wherein said connecting column comprises a plurality of substantially X-like struts disposed along the length of said connecting column, said struts being arranged between a pair of side-walls.

5. The bumper support column as claimed in claim 4, wherein at least one portion of said side-walls is substantially wave-shaped to facilitate controlled collapse thereof during a vehicle collision.

6. The bumper support column as claimed in claim 1, wherein said one-piece die-casting includes vehicle and bumper screw attachment holes.

7. The bumper support column as claimed in claim 2, wherein said alloy is AM60.

8. An energy-absorbing support column for a vehicle bumper substantially as described hereinbefore and with reference to the accompanying drawings.