Efficient joint for vehicle energy-absorbing device

A vehicle having an energy-absorbing device mountable to a bumper of the vehicle is provided. The energy-absorbing device is attached to a vehicle rail having an inner rail surface and an edge surface. The energy-absorbing device defines a first crush surface interfacing with the inner rail surface. In a first embodiment, the energy-absorbing device defines a second crush surface positioned to directly interface with the edge surface of the vehicle rail in the event of an impact. The energy-absorbing device is configured to transmit load received from the impact directly to the edge surface of the vehicle rail through the second crush surface. This results in an efficient joint for the energy-absorbing device.

TECHNICAL FIELD

The invention relates in general to a vehicle with an energy-absorbing device mountable to a bumper of a vehicle.

BACKGROUND OF THE INVENTION

An energy-absorbing device, sometimes referred to as a crush box, is sometimes attached to a vehicle bumper so that in the event of a low-speed impact event, the energy-absorbing device deforms longitudinally, confining the damage to the energy-absorbing device. A low-speed impact event generally occurs at a velocity of approximately 10 miles per hour or less. In some designs, the energy-absorbing device transfers the load from an impact through a plate welded onto the end of the energy-absorbing device to a plate welded onto the end of the motor compartment rail. The presence of plates at the joint adds mass and takes up packaging space in the vehicle.

SUMMARY OF THE INVENTION

A vehicle having an energy-absorbing device mountable to a bumper of the vehicle is provided. The energy-absorbing device is attached to a vehicle rail having an inner rail surface and an edge surface. The energy-absorbing device defines a first crush surface interfacing with the inner rail surface. In a first embodiment, the energy-absorbing device defines a second crush surface configured to directly interface with the edge surface of the vehicle rail in the event of an impact. In the first embodiment, there is a gap between the second crush surface and the edge surface in the absence of an impact event. In a second embodiment, the second crush surface directly interfaces with the edge surface of the vehicle rail, both in the absence and presence of an impact event. The energy-absorbing device is configured to transmit load received from an impact directly to the edge surface of the vehicle rail through the second crush surface. This results in an efficient joint for the energy-absorbing device.

The energy-absorbing device may be configured to compress against the vehicle rail during the impact event. The vehicle rail may be configured to be stronger than the energy-absorbing device and resist the load, thereby causing the energy-absorbing device to deform. The energy-absorbing device and the vehicle rail may extend in a direction parallel to a forward travel direction of the vehicle. The vehicle rail may be formed from two metal sheets attached together or from a unitary metal sheet. Grooves may also be formed on the vehicle rail. The second crush surface may extend substantially about a perimeter of the energy-absorbing device.

The energy-absorbing device may include first, second and third portions. The second portion may be oriented approximately perpendicularly with respect to the first and the third portions. The third portion of the energy-absorbing device may abut the inner rail surface. The energy-absorbing device may include at least one indentation configured to aid in an efficient longitudinal crush. The indentations serve to weaken the crush can at the site of the indentations, to enable an accurate prediction of where the deformation will occur during an impact event.

A bulkhead may be placed inside a cavity defined by the energy-absorbing device. The bulkhead prevents the crush can from collapsing on itself during an impact event. The bulkhead may include a central portion and at least one tab extending from the central portion. The tab may be angled with respect to the central portion. The bulkhead may be sufficiently fitted into the cavity such that the tab is attached to an inner surface of the energy-absorbing device. Ribs may be formed on the central portion of the bulkhead. The bulkhead may include first and second tabs extending at respective angles from the central portion. The first and second tabs may be operatively connected to the energy-absorbing device and the vehicle rail at the first crush surface and the inner rail surface, respectively.

At least one bolt may operatively connect the vehicle rail, the energy-absorbing device and the first and second tabs of the bulkhead. A first reinforcement plate may be placed inside a cavity defined by the energy-absorbing device. The first reinforcement plate may include a middle section and at least one side section. The side section may be angled with respect to the middle section. The side section may be attached to the energy-absorbing device at the inner surface of the energy-absorbing device. A second reinforcement plate may be connected to the energy-absorbing device and placed inside the cavity of the energy-absorbing device.

Thus, an energy-absorbing device with an integrated design is provided, without requiring any plates or brackets welded onto the end of the vehicle rail. The load is directly applied to the end of the vehicle rail, creating an efficient load path for load transfer, while reducing mass, cost, components, and increasing packaging space. The configuration also provides increased local stiffness to the end of the vehicle rail in the cross car direction, i.e., transverse to the direction of forward travel. This has been shown to improve dynamic stiffness at the front cradle attachments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1Ais a schematic plan cross-sectional view of an energy-absorbing device, referred to herein as a crush can10.FIG. 1Bis an enlarged view of the portion1B ofFIG. 1A.FIG. 2is a schematic perspective fragmentary view of the crush can10, whileFIG. 3is a schematic fragmentary perspective cross-sectional view of the crush can10.FIG. 4is a schematic rear perspective view of the energy-absorbing device shown inFIG. 1A

The crush can10includes a body12defining an opening14, shown inFIGS. 1A and 2. The body12is attached to a bumper16of a vehicle18at the opening14, as shown inFIG. 1A. The forward travel direction D of the vehicle18is shown inFIGS. 1A,2,3and4. The body12of the crush can10extends in a direction substantially parallel to the forward travel direction D. The crush can10defines a cavity20, shown inFIG. 1A.

A first reinforcement plate22is placed inside the cavity20, as shown inFIGS. 2 and 3. A second reinforcement plate24may also be added. The reinforcement plates22,24help to maintain a constant energy absorption rate through the body12of the crush can10. As shown inFIGS. 2 and 3, the first and second reinforcement plates22,24include side sections22a,24a, respectively, and middle sections22b,24b, respectively. The side sections22a,24aare oriented approximately perpendicularly with respect to the middle sections22b,24bof the reinforcement plates22,24, respectively. The side section22aof the first reinforcement plate22is welded or mechanically attached to the inner surface28of the body12of the crush can10, as best shown inFIG. 3. The side section24aof the second reinforcement plate24is also similarly attached to the inner surface28of the crush can10. The reinforcement plates22,24may be composed of a metal or any other suitable material. The configuration of the first and second reinforcement plates22,24may be varied in any suitable manner.

The crush can10also includes one or more indentations32(shown inFIGS. 1A,2,3and4) across the body12to enable the crush can10to more efficiently absorb energy and deform or crush. The indentations32serve to weaken the crush can10at the site of the indentations32. This enables an accurate prediction of where the deformation will occur during an impact event.

The crush can10is attached to a vehicle rail, such as the motor compartment rail36shown inFIGS. 1A,2and3. The end of the motor compartment rail36may be attached to the dash panel (not shown) of the vehicle18. The motor compartment rail36extends in a direction parallel to the forward travel direction D. The outer surface37of the motor compartment rail36is also shown inFIGS. 1A,2and3.

As noted above,FIG. 1Bis an enlarged view of the portion1B ofFIG. 1A. The crush can10includes first, second and third portions12a,12band12c, respectively, shown inFIG. 1B. The second portion12bjuts inward and is oriented approximately perpendicularly with respect to the first and third portions,12a,12c, respectively. The third portion12cof the crush can10is at least partially nested in and abuts the motor compartment rail36.

As shown inFIG. 1B, a first crush surface40of the crush can10interfaces directly with the inner rail surface42of the motor compartment rail36. That is, the crush surface40is in direct contact with the inner rail surface42. In a first embodiment, a second crush surface44of the crush can10is positioned to interface directly with the edge surface46of the motor compartment rail36in the event of an impact, as shown inFIG. 1B. In the first embodiment, there is a gap47between the second crush surface44and the edge surface46of the motor compartment rail36in the absence of an impact event, as shown inFIG. 1B.

The crush can10is configured to transmit load received from the impact event directly to the edge surface46of the motor compartment rail36through the second crush surface44, causing the crush can10to deform. The deformed profile48(in phantom) inFIG. 1Ashows the deformation of the crush can10in the event of a low-speed impact event. As noted above, a low-speed impact event generally occurs at a velocity of approximately 10 miles per hour or less. This is one possible configuration for the deformation, however not all crush cans may deform in this manner. The dimples49(shown inFIG. 1A) in the deformed profile48correspond to the indentations32in the crush can10. As noted above, the indentations32serve to weaken the crush can10at the site of the indentations32, resulting in deformations at the site of the indentations32.FIG. 1Bshows the deformed profile48of the crush can10at the second crush surface44, as it deforms and interfaces with the edge surface46of the motor compartment rail36during an impact event. The motor compartment rail36does not generally deform in a low speed impact event, however it may deform in a high speed impact event.

FIG. 4is a schematic rear perspective view of the crush can10, showing a bulkhead50(also shown inFIGS. 1A and 3) placed inside the cavity20of the crush can10. The motor compartment rail36is not shown inFIG. 4for clarity. The bulkhead50prevents the crush can10from collapsing on itself during an impact event. The bulkhead50includes a plurality of tabs arranged symmetrically around a central portion60, shown inFIG. 4. First and third tabs54,56are shown inFIG. 4. A second tab58is across from the first tab54, as shown inFIGS. 1A and 3. A fourth tab (hidden from view inFIG. 4) is formed across from the third tab56.

The first, second and third tabs54,58,56are angled with respect to the central portion60. Alternatively, the tabs may be oriented approximately perpendicularly with respect to the central portion60. The bulkhead50is fitted into the cavity20such that the first, second and third tabs54,58,56(as well as the fourth tab) may be welded or mechanically attached to the inner surface28(shown inFIGS. 1A,3and4) of the body12of the crush can10. The central portion60may be formed with ribs62for sturdiness of the bulkhead50. The bulkhead50may be composed of a metal or any other suitable material. The configuration of the bulkhead50and the tabs may be varied in any suitable manner.

FIG. 4shows the second crush surface44formed as a raised area of the body12, extending throughout the perimeter63of the body12of the crush can10. Alternatively, the second crush surface44may be formed as a raised area only at certain portions of the perimeter63. The length L1of the crush can10is nested in the motor compartment rail36, shown inFIGS. 1A and 4. As noted above, the motor compartment rail36is not shown inFIG. 4for clarity.

Bolts may be used to attach the motor compartment rail36to the crush can10and the bulkhead50. Any other suitable methods of connecting the motor compartment rail36, the crush can10and the bulkhead50may be used, e.g., adhesive, rivets or other mechanical fasteners.FIG. 4shows bolts64a,64bon one side of the motor compartment rail36and bolts66a,66bon the other side. As shown inFIG. 1A, bolt66bgoes through the motor compartment rail36, the crush can10(at the first crush surface40) and the first tab54. As shown inFIG. 1A, bolt64bgoes through the motor compartment rail36, crush can10(at the first crush surface40) and the second tab58. Bolts64aand64bare also shown inFIG. 2, while bolt64b,66bare also shown inFIG. 3.

The energy-absorbing device10may be composed of a metal such as steel or aluminum or any other suitable material. The motor compartment rail36may include two metal sheets68,70(shown inFIG. 2) that are welded or mechanically attached through any suitable method. Any other suitable configuration for the motor compartment rail36may be used. For example, the motor compartment rail36may be composed of one unitary piece of sheet metal with no welding, formed by hydroforming or other suitable methods. The motor compartment rail36may also be formed with grooves72, shown inFIGS. 1A and 2). The grooves72serve to initiate deformation in high speed impact events, i.e., they weaken the motor compartment rail36at the site of the grooves72in high speed impact events. The motor compartment rail36may be composed of a metal composite, aluminum, steel or any other suitable material. The configuration of the motor compartment rail36may be varied in any suitable manner.

In the event of an impact, the crush can10absorbs the energy of the impact event. The load is transferred through the body12of the energy-absorbing device or crush can10and directly applied to the motor compartment rail36, through the first and second crush surfaces40,44. Most of the impact load is transferred through the second crush surface44to the edge surface46of the motor compartment rail36. There are no intermediate plates between the surfaces44,46, creating an efficient load path. Without intermediate plates, the overall mass of the crush can10is reduced and the crush can requires less packaging space.

The crush can10uses the motor compartment rail36to initiate its crush, i.e., when the crush can10is compressed against the motor compartment rail36, the motor compartment rail36resists the energy and causes the crush can10to deform longitudinally. The motor compartment rail36is designed to be stronger than the crush can10. Through the use of different materials and/or changes in thicknesses (gauge), the motor compartment rail36may be configured to be stronger than the crush can10. For example, the motor compartment rail36may be made using steel of a higher grade than the crush can10. Alternatively, thicker sheet metals may be used to form the motor compartment rail36, compared to the crush can10. Making the motor compartment rail36stronger than the crush can10may be achieved in many other ways as well, e.g., variations in the shape of the motor compartment rail36with respect to the crush can10, the use of additional reinforcements, and other methods.

Second Embodiment

A second embodiment is shown inFIG. 5, with a crush can110.FIG. 5shows the same view asFIG. 1B, which is an enlarged view of the portion1B ofFIG. 1A. In the second embodiment, a second crush surface144directly contacts an edge surface146of the motor compartment rail136with no gap therebetween. In the second embodiment, the profile of the crush can110would remain the same at the second crush surface144in the event of an impact, since the second crush surface144is already in direct contact with the edge surface146of the motor compartment rail136. Thus the second crush surface144directly interfaces with the edge surface146, both in the absence and presence of an impact event. The crush can110is configured to transmit load received from the impact directly to the edge surface146of the motor compartment rail136through the second crush surface144. This results in an efficient joint for the crush can110.

The first crush surface140of the crush can110continues to interface directly with the inner rail surface142of the motor compartment rail136.FIG. 5shows the first, second and third portions112a,112band112c, respectively, of the crush can110. Similar toFIG. 1B,FIG. 5also shows a tab154of a bulkhead150(partially shown) that is placed in a cavity defined by the crush can110.