Abstract:
A hydroforming system includes a dual conical tube formed from a blank. The dual conical tube has a first end, a second end and a central portion positioned between the first and the second ends. The central portion has a smaller cross sectional area than the first and the second ends. A shaping die is adapted to receive the dual conical tube, and the shaping die is subject to pressurize such that the tube substantially approximates the shape of the shaping die.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates generally to processes for molding automotive components and, more particularly, to a method for hydroforming component specific blanks.  
       BACKGROUND ART  
       [0002]     Hydroforming is a metal forming process through which metal tube blanks are formed into shapes, such as automotive body components, through the application of internal water hydraulic pressure.  
         [0003]     Standard hydroforming techniques start with a sheet of metal or a bent tube. Hydroforming differs from conventional deep drawing processes by replacing die tools with rubber diaphragms, which are backed with fluid pressure, to form punch tool components.  
         [0004]     Relating the aforementioned concept to tubular parts, a tube is placed in a die, then the tube is filled with a fluid pressure to form a part to the die. In other words, the tube blanks are reshaped through cross-sectional changes along the length of the tube blanks.  
         [0005]     Low pressure sheet forming, through which the tube is filled with a low pressure fluid that forms the part to the die, is ideal for parts with large radii, simple cross sections, and flat surfaces. High pressure sheet forming is ideal for parts requiring complex cross sections with small radii. The drawback to high pressure forming is that, due to friction, parts tend to have non-uniform thickness.  
         [0006]     For active hydroforming, the part is placed in the hydroforming press. Before the press is cycled shut, a fluid pressure is applied to expand the part while maintaining the metal at a uniform thickness. The resulting part tends to have uniform thickness even for complex cross sections. Active hydroforming takes the strong points from high and low pressure hydroforming and combines them into a single process.  
         [0007]     The hydroforming process allows close control of parameters (e.g. fluid pressure and lubrication) to prevent wrinkling and tearing of parts. High quality parts that are substantially hard, resistant to buckling and unlikely to have surface defects are produced through hydroforming. Improved process flow also tends to result from decreased die wear due to fluid on metal forming rather than metal on metal forming.  
         [0008]     Hydroforming flows metal rather than stretching it. Therefore, thinning of material is minimal. This often results in material savings because thinner blanks can be used, which is an important factor in decreasing costs when expensive alloys are required or a large number of parts are ordered.  
         [0009]     The existing stamped shape of a front rail for a unitized body has the end that the bumper attaches to flared open initially and gradually decreased in cross sectional dimensions as the rail bypasses the tire envelope on one side and powertrain on the other side. Once past the tire envelope and powertrain, the section is again increased in cross sectional dimensions as it transitions to the dash. Replacing the front stamped rail with a regular tube shape hydroformed rail requires end feeding into a hydroform press to get expansion near the ends during a hydroforming process, and this method of feeding tends to limit the degree of conical shape, which is needed for automobile body engineering requirements.  
         [0010]     The limitation associated with current component molding techniques has made it apparent that a modified technique to mold components is necessary. The modified technique should substantially minimize steps required for a hydroforming process and should facilitate compliance with automobile body engineering requirements. The present invention is directed to these ends.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention provides a method for hydroforming component specific blanks. The present invention also provides a hydroforming system that incorporates component specific blanks and a tube designed to efficiently receive and facilitate molding of the component specific blanks.  
         [0012]     One aspect of the present invention includes a method for molding a part comprising: rolling a substantially bow tie shaped blank lengthwise to form a dual conical tube, said dual conical tube comprising a first end, a second end and a central portion positioned between said first and said second ends; inserting said dual conical tube in a metal forming device comprising a shaping die; and substantially forming through pressurization said substantially bow tie shaped blank to an approximate shape of said shaping die.  
         [0013]     In accordance with another aspect of the present invention, a system for hydroforming, including a dual conical tube formed from a blank is disclosed. The dual conical tube has a first end, a second end and a central portion positioned between the first and the second ends. The central portion has a smaller cross sectional area than the first and the second ends. A shaping die is adapted to receive the dual conical tube and is subject to pressurize such that the blank substantially conforms to a shape of the shaping die.  
         [0014]     One advantage of the present invention is that it facilitates efficient and versatile shaping of automotive body components. Another advantage is a decrease of package space required due to the narrow cross-section in the central portions of components manufactured from the aforementioned process. Still another advantage is the elimination of the need to add localized reinforcements due to the larger cross sectional area at the end sections.  
         [0015]     Additional advantages and features of the present invention will become apparent from the description that follows and may be realized by the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1   a  is an exploded view of a hydroforming system in accordance with an embodiment of the present invention;  
         [0017]      FIG. 1   b  is a cross-sectional view of the assembled hydroforming system of  FIG. 1   a  in the direction of line  1   b - 1   b;    
         [0018]      FIG. 1   c  is a perspective view of the bow tie shaped blank and the dual conical tube of  FIG. 1   a;    
         [0019]      FIG. 2  is a perspective view of a substantially bow tie shaped part manufactured through operation of the system of  FIG. 1   a  in accordance with an embodiment of the present invention; and  
         [0020]      FIG. 3  is a block diagram of a method for hydroforming in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0021]     The present invention is illustrated with respect to a method for molding a component, particularly suited to the automotive field. The present invention is, however, applicable to various other uses that may require hydroformed components, as will be understood by one skilled in the art.  
         [0022]     Referring to  FIGS. 1   a ,  1   b , and  FIG. 2 , a dual conical tube  14  for use in a hydroforming method  10 , including a substantially bow tie shaped blank  12 , is disclosed. The blank  12  is adapted to be rolled to form the dual conical tube  14 . The blank  12  is here illustrated as a substantially bow tie shaped blank  12 , however, it is to be understood that numerous alternate blank shapes may be used depending on specific part parameters, as one skilled in the art would realize.  
         [0023]     The substantially bow tie shaped blank  12  is reinforced, depending on material and tensile requirements for the blank  12  prior to the rolling and forming processes, as will be discussed later. Alternate embodiments of the present invention include two separate ends of the blank  12  whereby joining the two ends  28 ,  30  at the central portion  32 , the substantially bow tie shaped blank  12  is assembled.  
         [0024]     The blank  12  is rolled to form the dual conical tube  14 , as will be understood by one skilled in the art. The tube is then welded at seams along the length of the tube between the tube ends  34 ,  38 , and for product components requiring further bending, the tube is bent to facilitate hydroforming of the desired part  20 . A shaping die  16 , located within a die frame  17  and coupled to a hydroforming press  18 , is adapted to receive the dual conical tube  14 . The hydroforming operation then cycles, and a dual conical shaped part  20  is formed. One embodiment of a part  20  formed from the aforementioned method  10  is illustrated in  FIG. 2 .  
         [0025]     Manufacturing a dual conical shaped part  20  from a single blank  12  allows a larger cross sectional diameter at the ends of the part  20  (first end  22  and second end  24 ) and a narrow cross sectional diameter between the ends (central portion  26 ) and thereby accommodates packaging and energy management requirements, as will be understood by one skilled in the art. This also reduces need for localized reinforcements due to the enlarged cross sectional diameter at the ends  22 ,  24 .  
         [0026]     Referring to  FIG. 1   c , a perspective view of the bow tie shaped blank  12  and the dual conical tube  14  of  FIG. 1   a  is illustrated. The bow tie blank  12  is a substantially flat sheet of metal such as aluminum, though alternate flexible metals may be molded using the aforementioned method. The blank  12  is embodied as having two ends  28 ,  30  linked by a substantially smaller central portion  32 . The sheet is either cut as a single piece or is the combination of a number of sheets greater than one welded together, as will be understood by one skilled in the art.  
         [0027]     Reinforcements are welded to the substantially bow tie shaped blank  12  in the form of patches prior to the rolling and forming operation, as will be understood by one skilled in the art. The tailored sheet blank (bow tie blank  12 ) is alternately constructed using materials of varied thickness, as is well understood, for energy management.  
         [0028]     The dual conical tube  14  necks down from one end (first end  34 ) to a minimum point (central point  36 ) then expands back out towards the other end (second end  38 ).  
         [0029]     The dual conical shape blank (bow tie blank  12 ), which is rolled to form the dual conical tube  14 , allows the hydroforming process to deliver a shape suited to match engineering energy management requirements for front crash while minimizing weight and additional reinforcements on, for example, hydroformed front rails.  
         [0030]     The dual conical tube  14  is welded at the seam along the length of the tube through a well known joining method (e.g. Gas Metal Arc Welding, Tungsten Inert Gas, Laser Welding, electron beam welding, hybrid (laser-GMAW or laser-plasma) welding, friction stir welding or seam mesh welding).  
         [0031]     The dual conical tube  14  is post processed by a tube bending operation prior to hydroforming, as one skilled in the art would realize, for components requiring bending beyond hydroforming capabilities.  
         [0032]     After the dual conical tube  14  is sealed and bent, the shaping die  16  pressurizes the dual conical tube  14  such that it substantially conforms to a shape of the shaping die  16 .  
         [0033]     The existing stamped shape of a front rail for a unitized body has an end, that the bumper attaches to, flared open initially and gradually decreased as the rail bypasses the tire envelope on one side and powertrain on the other side. Once past the tire envelope and the powertrain, the section again increases as it transitions to the dash. Replacing the front stamped rail with a regular tube shape hydroformed rail requires end feeding of both ends individually into a hydroform press to get expansion near the ends, during the hydroform process. This former method of feeding limits the degree of conical shape, which is needed for automobile body engineering requirements.  
         [0034]     Referring to  FIG. 3 , a block diagram of a method for hydroforming is disclosed. The method starts in inquiry block  40 , when an inquiry is made as to whether the bow tie blank requires reinforcement. For a positive response, the bow tie blank is reinforced in operation block  42  prior to activation of operation block  43 , as was mentioned earlier.  
         [0035]     Otherwise in operation block  43 , the blank is rolled to form a dual conical tube.  
         [0036]     Operation block  44  then activates, and the edges of the blank are joined together to form the dual conical tube.  
         [0037]     An inquiry is then made in block  46  as to whether the dual conical tube requires further bending to achieve the component shape. For a positive response, operation block  48  activates, and the tube is bent according to component specifications, prior to activation of operation block  50 .  
         [0038]     Otherwise, operation block  50  activates, and the dual conical tube is inserted into the hydroforming press.  
         [0039]     The method concludes in operation block  54  when the bow tie blank is substantially formed to the component shape, as determined by the specific die type used for the hydroforming press.  
         [0040]     In operation, a substantially bow tie shaped blank is rolled to form a dual conical tube. The dual conical tube is inserted in a metal forming device having a shaping die. The dual conical tube is formed through pressurization to a shape determined from the die.  
         [0041]     From the foregoing, it can be seen that there has been brought to the art a new method for hydroforming. It is to be understood that the preceding description of the preferred embodiment is merely illustrative of some of the many specific embodiments that represent applications of the principles of the present invention. Numerous and other arrangements would be evident to those skilled in the art without departing from the scope of the invention as defined by the following claims.