Abstract:
A hydroformed member having internal reinforcements and method of manufacturing the same. The method includes the steps of providing a die having a tooling cavity and a pair of opposing rams disposed in the tooling cavity. A tubular member is enclosed within the tooling cavity. The pair of opposing rams are then driven against opposing sides of the tubular member to form a pair of opposing indentations therein. While the rams remain in place, hydraulic fluid pressure is then applied within the tubular member causing the walls of the tubular member to closely conform to the shape of the tooling cavity and the pair of opposing rams.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a hydroformed structural member and, more particularly, relates to a hydroformed structural member having internal hydroformed reinforcements and a method of making the same. 
     BACKGROUND OF THE INVENTION 
     It is well known, in the prior art, that the structural or mechanical characteristics of a support member may be improved with the addition of internal reinforcements. This practice is common in the use of stamp-formed members, wherein internal supports are secured, typically by welding, to the stamp-formed member to provide additional localized loading capabilities. However, with the increased popularity and dimensional accuracy of hydroforming, there has been a growing trend to provide additional sectional stiffness as needed for localized loading. 
     By way of review, hydroforming is essentially the process of deforming a tubular member to a desired complex tubular shape. To this end, the tubular member is placed between a pair of dies having cavities which define the desired resultant shape of the tube. The ends of the tubular member are accessible through the die and a seal is connected to the ends of the tubular member. Pressurized fluid is then injected into the ends of the tubular member, thereby forcing the tubular member to expand and conform to the shape defined by the die cavity. 
     To provide additional sectional stiffness in hydroformed members, attempts have been made to form hydroformed members having varying wall thickness. This is typically accomplished by welding multiple tubular sections having varying wall thickness together to form a tubular blank. The tubular blank is then hydroformed to produce a member having additional localized stiffness. However, this method is relatively time-consuming and requires additional process steps of assembling and welding the tubular blanks. Lastly, the additional processing steps may further limit the ability to mass produce such items cost effectively. 
     Accordingly, there exists a need in the relevant art to provide a method of simply and conveniently forming a hydroformed structural member capable of providing additional sectional stiffness while, simultaneously, minimizing the necessary process steps. Furthermore, there exists a need in the relevant art to provide a method of forming a member having internal hydroformed reinforcements. Still further, there exists a need in the relevant art to provide a hydroformed member having internal reinforcements. 
     SUMMARY OF THE INVENTION 
     In accordance with the broad teachings of this invention, a hydroformed member having internal reinforcements is provided having an advantageous construction and method of manufacturing the same. The method comprises the steps of providing a die having a tooling cavity and a pair of opposing rams disposed in the tooling cavity. A tubular member is enclosed within the tooling cavity. The pair of opposing rams are then driven against opposing sides of the tubular member to form a pair of opposing indentations therein. While the rams remain in place, hydraulic fluid pressure is then applied within the tubular member causing the walls of the tubular member to closely conform to the shape of the tooling cavity and the pair of opposing rams. 
     The present invention enables internal reinforcements to be hydroformed within a member to provide improved crash energy management and/or improved load bearing characteristics. The present invention is accomplished in a minimum number of process step, thereby minimizing manufacturing time and complexity and further reducing manufacturing costs. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a hydroformed structural member having internal hydroformed reinforcements according to the present invention; 
     FIG. 2 is a cross sectional view of FIG. 1, taken along line  2 — 2 ; 
     FIGS. 3-8 illustrate progressive steps in forming the internal hydroformed reinforcements in the hydroformed structural member; and 
     FIG. 9 illustrates an alternative embodiment of the hydroforming die. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For example, the techniques disclosed herein may have utility in forming a wide variety of different hydroformed parts. 
     Referring to the drawings, a hydroformed structural member  10 , and a method of making the same, is provided for use in various load bearing applications. Hydroformed structural member  10  is hydroformed from a single, continuous, tubular member. As best seen in FIG. 1, hydroformed structural member  10  includes a plurality of depressions or indentations  12  disposed along opposing sidewalls  14  of hydroformed structural member  10 . Each of the plurality of indentations  12  is shown generally having an inwardly projecting, arcuate bulge  16 . 
     As best seen in FIG. 2, the plurality of indentations  12  are positioned along hydroformed structural member  10  to define generally opposing pairs of indentations  12 . Each pair of indentations  12  are positioned along hydroformed structural member  10  to provided crash energy management and further provide additional sectional stiffness as needed for localized loading. Preferably, each pair of indentations  12  are secured together at a point of contact  18  to provide further structural integrity, although this is not required. This point of contact  18 , as seen in FIG. 2, preferably occurs at an internal apex  20  of inwardly projecting, arcuate bulge  16 . Each pair of indentations  12  may be secured at point of contact  18  via a weld  22 . However, it should be appreciated that each pair of indentations  12  may be secured together by any known method that provides a reliable connection. Each pair of indentations  12  defines an internal hydroformed reinforcement  24  within hydroformed structural member  10 . 
     According to a preferred method of forming hydroformed structural member  10  and internal hydroformed reinforcements  24 , a straight tube  26  having uniform wall thickness is first provided. Generally, straight tubes are readily available in the marketplace to facilitate mass production of hydroformed structural member  10  with internal hydroformed reinforcements  24 . 
     Preferably, as seen in FIGS. 3-4, straight tube  26  is preformed into a generally oblong member  28  having a slightly reduced cross-sectional width A relative to an end width B. It should be appreciated, however, that straight tube  26  may be simply hydroformed, without the need to preform the member, depending upon the required physical and mechanical characteristics of the application. 
     During the hydroforming process as seen in FIGS. 5-8, oblong member  28  is first disposed in a hydroforming die  30 . Hydroforming die  30  generally includes an upper die member  32  and a lower die member  34 . Upper die member  32  and lower die member  34  include opposing surfaces  36 ,  38  respectively. Opposed surfaces  36  and  38  are contoured, aligned, and spaced to define a tooling cavity  40 . Hydroforming die  30  further includes a plurality of fluid inlet ports (not shown) adapted to deliver a hydraulic fluid  42  (FIG. 7) under extreme pressure, typically in the range of 10,000 to 30,000 psi, to an interior volume  44  of oblong member  28 . 
     As best seen in FIGS. 5-8, hydroforming die  30  further includes a plurality of rams  46 . Rams  46  are each adapted to be disposed between upper die member  32  and lower die member  34  of hydroforming die  30 . However, it should be appreciated that rams  46  may be disposed in any orientation in hydroforming die  30 . Rams  46  are each selectively actuated or driven to extend past an internal surface  48  of tooling cavity  40  and against opposing sidewalls  50  of oblong member  28 . 
     During manufacturing, oblong member  28  is placed in tooling cavity  40  of hydroforming die  30 . Oblong member  28  generally follows the contour shape of tooling cavity  40  of hydroforming die  30 , yet is smaller in width and height to accommodate hydroforming. Oblong member  28  is then enclosed within hydroforming die  30  as seen in FIG.  5 . The slightly reduced cross-sectional dimension of oblong member  28  relative to tooling cavity  40  of hydroforming die  30  defines a gap  52  generally surrounding oblong member  28 . Gap  52  generally represents the difference in cross-sectional dimensions between the current oblong member and the final preferred member. The hydraulic fluid injectors are then coupled to the ends of oblong member  28  to provide a fluid seal between interior volume  44  of oblong member  28  and a hydraulic fluid pressure source (not shown). 
     Referring to FIG. 6, rams  46  are then actuated and/or driven against sidewalls  50  of oblong member  28 . The force of rams  46  driving against sidewalls  50  of oblong member  28  forces sidewalls  50  to inwardly deform in response thereto. It should be appreciated that the first position of rams  46  may be such that the rams allow movement of oblong member  28  within tooling cavity  40  to enable proper positioning of oblong member  28  to be achieved automatically during hydroforming. It should further be appreciated that the initial position of rams  46  further enables localized stretching of oblong member  28  during the hydroforming process. By way of example, following the actuation of rams  46 , sidewalls  50  define a cross-sectional dimension C, which is smaller than cross-sectional dimension A. 
     Referring to FIG. 7, hydraulic fluid  42  is then introduced into interior volume  44  of oblong member  28  such that oblong member  28  expands to closely conform to the shape of tooling cavity  40  of hydroforming die  30  and to the shape of rams  46 . Pressurized hydraulic fluid  42  forces sidewalls  50  outward to form the preferred profile of hydroformed structural member  10 . Finally, referring to FIG. 8, rams  46  are further actuated and/or driven against sidewalls  50  of oblong member  28  during continued application of hydraulic fluid  42 . Preferably, rams  46  are driven until sidewalls  50  of oblong member  28  are substantially in contact, thereby defining point of contact  18 . This method thereby forms internal hydroformed reinforcements  24 . 
     It is anticipated that rams  46  may be welding electrodes to enable point of contact  18  to be welded while member  28  is disposed in hydroforming die  30 . To this end, each ram  46  is coupled to a welding device  51  (FIG. 8) that is capable of welding member  28 . 
     Alternatively, as seen in FIG. 9, rams  46   b  may be fixedly secured or integrally formed with upper die cavity  32   b  and lower die cavity  34   b . During manufacturing, internal hydroformed reinforcement  24   b  are initially formed during closure of upper die cavity  32   b  and lower die cavity  34   b . Subsequent introduction of hydraulic fluid  42  forces sidewalls  50   b  to closely conform to tooling cavity  40   b . Such arrangement simplifies the hydroforming die. Preferably, a point of contact  18   b  is achieved to facilitate fastening of indentations  12   b.    
     Referring to FIG. 2, internal hydroformed reinforcement may then be secured together via weld  22  to provide improved structural loading and integrity. Moreover, additional external supports, such as a coverplate  54  and/or a bracket  56  may then be fastened to an exterior portion  58  of hydroformed structural member  10 . Preferably, coverplate  54  and bracket  56  are secured to hydroformed structural member  10  at a position directly over each of the plurality of indentations  12  to provide further improved structural integrity. 
     It should be appreciated that the hydroformed structural member having internal hydroformed reinforcements of the present invention provides a unique and novel member for use in load bearing applications, which is simply and conveniently formed in a single hydroforming process. Moreover, the hydroformed section is essentially intact during the complete hydroforming process, thus ensuring dimensional integrity. Distortion due to welding on the side plates can be minimized by welding them simultaneously. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention. Such variations or modifications, as would be obvious to one skilled in the art, are intended to be included within the scope of the following claims.