The invention relates to a motor compartment rail assembly for a motor vehicle.
The motor compartment of a vehicle is often configured with an energy absorbing device, sometimes referred to as a crush box, located between a bumper and a longitudinally-extending motor compartment rail. The crush box is configured to deform in the event of an impact force on the bumper, to minimize deformation and energy transfer rearward to the motor compartment rail. Depending on the magnitude of the impact energy, the motor compartment rail may also deform. It is desirable to control the deformation in an axial (fore-aft) direction. Thin-walled motor compartment rails that have a “tall aspect ratio”, i.e., a relatively large height to transverse width ratio, are more susceptible to deformation in other than a fore-aft direction than thicker walled rails or rails with a lower aspect ratio. Adding wall thickness is one solution, but this adds weight to the vehicle, increases the rail cross-section size, and affects packaging.
A motor compartment rail assembly is provided that enhances stability of a motor compartment rail, and is especially useful in stabilizing relatively thin-walled, tall aspect ratio rails to prevent deformation in which the rail pivots laterally inward or outward (i.e., “Z-moment” deformation) without adding significant weight.
Specifically, a rail assembly for a motor compartment of a motor vehicle having a bumper and a deformable energy-absorbing device secured rearward of the bumper, includes a longitudinally-extending motor compartment rail operatively connected rearward of the energy absorbing device and having an inner rail member and an outer rail member configured to define a cavity therebetween. A stability enhancement member transversely spans the cavity and is secured to both the inner rail member and the outer rail member. Preferably, the stability enhancement member is secured to inner surfaces of the inner and outer rail members generally perpendicular to the inner surfaces. The stability enhancement member may be configured with corrugations extending at least partway between the inner and outer rail members. The stability enhancement member may be positioned immediately rearward of a joint that establishes an interface between the energy absorbing device and the rail member, or may be positioned further rearward of the joint, such as between the joint and a cradle mount joint further rearward of the interface joint.
Accordingly, a method of assembling a motor compartment rail having an inner rail member and an outer rail member as described above includes securing a stability enhancement member to both the inner rail member and the outer rail member to transversely span a cavity defined therebetween.
The securing of the stability enhancement member may be by welding the stability enhancement member to an inner surface of one of the inner and outer rail members, and, after the welding, securing the inner rail member to the outer rail member to enclose the stability enhancement member within a cavity formed therebetween. The stability enhancement member is then welded to the other of the inner and outer rail members from outside of the cavity. Apertures may be formed in the rail aligned with the stability enhancement member to ensure that the welding occurring after the stability enhancement member is enclosed between the rail members is directed to the stability enhancement member.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
Referring to the drawings, wherein like reference numbers refer to like components throughout the several views,
The rail assembly 12 includes an inner rail member 26 extending longitudinally rearward from the joint interface 18. The rail assembly 12 also includes an outer rail member 30, which is removed in
As shown in
The rail assemblies 12 and 12A are each “tall aspect ratio” rail assemblies as the height H of the inner rail member 26 and the outer rail member 30 is at least twice the width W of the assembled inner and outer rail members 26, 30. Such tall aspect ratio rail assemblies have a tendency to deform by pivoting about a vertical axis, i.e., creating what is referred to by those skilled in the art as a “Z moment”.
Each of the stability enhancement members 28, 28A are secured approximately midway along the height H of the rail members 26, 30 and absorb energy, acting to increase Z-moment force capacity and delay such Z moment deformation, making the rail members 26, 30 more apt to deform in a fore/aft direction, which is preferable.
As shown in
In
A method 100 of assembling the rail assembly 12 of
After step 104, the method 100 proceeds to step 106, in which the inner rail member 26 is secured to the outer rail member 30. This substantially encloses the stability enhancement member 28 or 28A within the cavity 32 defined by the inner and outer rail members 26, 30. As described above, the rail members 26, 30 may be bolted or welded to one another, or may simply abut one another and be secured to nearby components, such as the interface joint 18 or the engine cradle 24.
After step 106, the stability enhancement member 28 or 28A can now be secured to the inner rail member 26 by MIG welding the components to one another from outside of the cavity 32 (i.e. from outside of the rail members 26, 30) through apertures 44 (shown in
While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
5868457 | Kitagawa | Feb 1999 | A |
6354654 | Lee | Mar 2002 | B2 |
6808039 | Roehringer et al. | Oct 2004 | B2 |
7066509 | Kollaritsch et al. | Jun 2006 | B2 |
7185945 | Dandekar et al. | Mar 2007 | B2 |
7270368 | Aonuma et al. | Sep 2007 | B2 |
Number | Date | Country |
---|---|---|
3826958 | Mar 1989 | DE |
1184263 | Mar 2002 | EP |
2002012164 | Jan 2002 | JP |
Number | Date | Country | |
---|---|---|---|
20100213725 A1 | Aug 2010 | US |