Abstract:
A method of progressive hydro-forming of a tubular member includes the steps of positioning a tubular member between open die halves mating with one another to define a first tubular cavity portion in a first stage. The method also includes the steps of progressively closing the die halves and applying hydraulic pressure to expand and conform the tubular member to the first tubular cavity portion in the first stage. The method includes the steps of positioning the expanded tubular member in a second tubular cavity portion in a second stage and progressively closing the die halves to progressively deform the expanded tubular member within the second tubular cavity portion. The method includes the steps of applying hydraulic pressure to expand and conform the expanded tubular member to the second tubular cavity portion in the second stage.

Description:
TECHNICAL FIELD 
     The present invention relates generally to forming a shaped tubular member and, more particularly, to a method of progressive hydro-forming of tubular members for automotive components. 
     BACKGROUND OF THE INVENTION 
     It is known to form a cross-sectional profile of a tubular member by a hydro-forming process in which a fluid filled tubular blank is placed within a die and then the die is closed so that the tubular blank is formed within the die. Fluid pressure is then increased inside the tubular member to expand the blank outwardly against the die cavity to provide a tubular component having a die formed cross-sectional profile. The tubular component may also have different cross-sectional profiles along the length thereof. 
     For an automotive component such as a fuel filler neck or manifold of a fuel fill system, the fuel filler neck and manifold are made with several pieces of deep drawn stampings and brazed together to form a leak-free tubular member of varying cross-section. This process results in a seam to be added so that the deep drawn stamping process could be used. However, the above-described hydro-forming process could not be used for the fuel filler neck and manifold because of the expansion requirements of the manifold sections. 
     As a result, it is desirable to provide a new method of hydro-forming a tubular member. It is also desirable to provide a method of hydro-forming a tubular member that allows smaller diameter tubes to be expanded significantly. It is further desirable to provide a method of hydro-forming a fuel filler neck or a fuel neck and manifold as one-piece. Therefore, there is a need in the art to provide a method of hydro-forming a tubular member that meets these desires. 
     SUMMARY OF THE INVENTION 
     It is, therefore, one object of the present invention to provide a new method of hydro-forming a tubular member. 
     It is another object of the present invention to provide a method of progressive hydro-forming of a tubular member. 
     To achieve the foregoing objects, the present invention is a method of progressive hydro-forming of a tubular member. The method includes the steps of providing a tubular member. The method also includes the steps of positioning the tubular member between open die halves mating with one another to define a first tubular cavity portion in a first stage. The method further includes the steps of progressively closing the die halves to progressively deform the tubular member within the first tubular cavity portion. The method includes the steps of applying hydraulic pressure to expand and conform the tubular member to the first tubular cavity portion in the first stage. The method also includes the steps of separating the die halves and removing the expanded tubular member from the first tubular cavity portion. The method also includes the steps of positioning the expanded tubular member between open die halves mating with one another to define a second tubular cavity portion in a second stage. The method further includes the steps of progressively closing the die halves to progressively deform the expanded tubular member within the second tubular cavity portion. The method includes the steps of applying hydraulic pressure to expand and conform the expanded tubular member to the second tubular cavity portion in the second stage. The method also includes the steps of separating the die halves and removing the tubular member from the second tubular cavity portion. 
     One advantage of the present invention is that a method of progressive hydro-forming of a tubular member is provided for a vehicle component, such as a fuel filler neck and manifold. Another advantage of the present invention is that the method allows the use of smaller diameter tubes, resulting in less cost and mass. Yet another advantage of the present invention is that the method improves part quality, eliminating brazing seams and allowing improved part repeatability. Still another advantage of the present invention is that the method reduces tooling expense. A further advantage of the present invention is that the method can produce an integral one-piece part, thereby eliminating several pieces of deep drawn stampings that are brazed together. 
     Other objects, features, and advantages of the present invention will be readily appreciated, as the same becomes better understood, after reading the subsequent description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a dual fuel tank simultaneous fill system incorporating a fuel filler neck and manifold made by a method, according to the present invention, of progressive hydro-forming of a tubular member. 
         FIG. 2  is a perspective view of a pre-formed tubular member for the fill system of  FIG. 1 . 
         FIG. 3  is an exploded perspective view of the pre-formed tubular member of  FIG. 2  placed between the halves of a die set and illustrating a first stage of progressive hydro-forming. 
         FIG. 4  is an exploded perspective view of the expanded tubular member of  FIG. 3  placed between the halves of a die set and illustrating a second stage of progressive hydro-forming. 
         FIG. 5  is an exploded perspective view of the pre-formed tubular member and expanded tubular member of  FIGS. 3 and 4  placed between the halves of a die set and illustrating the progressive hydro-forming. 
         FIG. 6  is a perspective view of one embodiment of the fuel filler neck and manifold of  FIG. 1 , which has been progressively hydro-formed to a desired shape. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings and in particular  FIG. 1 , one embodiment of a dual fuel tank simultaneous fill system  10  is generally shown for a vehicle (not shown). The fill system  10  includes a first fuel tank  12  and a second fuel tank  14 . The fill system  10  also includes a vapor relief line  16  fluidly connected to the first fuel tank  12  and the second fuel tank  14  from a first tank vent/overflow outlet  18  on the first fuel tank  12  to a second tank overflow inlet  20  on the second fuel tank  14 . The fill system  10  includes a vapor relief outlet  22  connected to the second fuel tank  14  and vented to atmosphere. 
     The fill system  10  further includes a first pump  24  that draws fuel only from the first fuel tank  10  and delivers it via a line  26  to an engine  28  of the vehicle. The fill system  10  includes a second pump  30  that transfers fuel via a line  32  from the second fuel tank  14  to the first fuel tank  12 . It should be appreciated that, as fuel is drawn from the first fuel tank  12 , the second pump  30  transfers fuel from the second fuel tank  14  to the first fuel tank  12 . 
     The fill system  10  includes a fuel filler neck and manifold assembly, generally indicated at  34 , to fill the first fuel tank  12  and second fuel tank  14  simultaneously. The fuel filler neck and manifold assembly  34  includes a fuel inlet line or filler neck  36  and a flow-directing manifold connector  38  connected to the fuel filler neck  36 . The manifold connector  38  has a generally “Y” shape to allow the first fuel tank  12  and second fuel tank  14  to be filled simultaneously. The fuel filler neck and manifold assembly  34  also includes a first tank branch line  40  interconnecting the manifold connector  38  and the first fuel tank  12  and a second tank branch line  42  interconnecting the manifold connector  38  and the second fuel tank  14 . The first fuel tank  12  is fluidly connected to the first tank branch line  40  through a first tank inlet opening  44 . The second fuel tank  14  is connected to the second tank branch line  42  by a second tank inlet opening  46 . 
     Referring to  FIG. 6 , the fuel filler neck  36  and the manifold connector  38  are formed as a monolithic structure, being integral, unitary, and one-piece. The manifold connector  38  includes an inlet port  48 , a first outlet port  50 , and a second outlet port  52 . The manifold connector  38  also includes a manifold section  54  with the inlet port  48  at an upper end thereof, and the outlet ports  50 ,  52  depend from a lower, horizontal wall or end cap  56  of the manifold section  54 . It should be appreciated that the first and second outlet ports  50  and  52  have substantially equal diameters. 
     The fuel filler neck  36  includes a fuel fill cup  58  and a bend neck  60  interconnecting the fuel fill cup  58  and the inlet port  48  of the manifold connector  38 . The fuel fill cup  58  and bend neck  60  have a plurality of ribs  62  formed therebetween. Preferably, four ribs  62  are formed. It should be appreciated that fuel filler neck  36  and manifold connector  38  allow simultaneous filling of the first fuel tank  12  and second fuel tank  14  for a vehicle without premature nozzle shut-off and/or fuel spit-back under all operating conditions and fuel characteristics. 
     The fuel filler neck  36  and manifold connector  38  are formed by a method, according to the present invention, of progressive hydro-forming. The fuel filler neck  38  and manifold connector  38  are formed as a tubular member being integral, unitary, and one piece. The end cap  56  is formed with several steps of a stamping. The end cap  56  with the two outlet ports  50 ,  52  is then brazed to the hydro-formed fuel filler neck  36  and manifold connector  38 . It should be appreciated that the first tank branch line  40  and second tank branch line  42  are joined to the manifold connector  38  by conventional means such as hoses and clamps. 
     Referring to  FIG. 2 , a tubular blank or member is shown for use in carrying out a method, according to the present invention, of progressively hydro-forruing a tubular member such as the fuel filler neck  36  and manifold connector  38 . The term “progressive hydro-forming” as used in this application means a two-stage die that enables a small tube to be expanded significantly. This two-stage die could be mounted to the press bed of a hydro-forming press. Alternatively, this two-stage die wit separate die cavities could be mounted in two separate presses. It should be appreciated that, although the method is described for the fuel filler neck and manifold connector  38 , the method can be used for progressive hydro-forming of other tubular members for components such as exhaust systems. 
     The method includes the step of providing a tubular member  69 . The tubular member  69  is made of a metal material. In one embodiment, the tubular member has a generally circular cross-sectional shape and extends axially. The method includes the step of bending the tubular member  69  to a predetermined position to form a pre-formed tubular member  70  with generally circular cross-sections. In the embodiment illustrated, the tubular member  69  has been bent to a predetermined position such as having a generally “L” shape through a suitable bending process such as mandrel bending, stretch bending, or die bending. It should be appreciated that the pre-formed tubular member  70 , as illustrated, has the same diameter circular cross-section throughout its length. It should also be appreciated that an optimum diameter of the tubular member  69  is selected based on manufacturing and product needs. 
     Referring to  FIGS. 3 through 5 , the method includes the step of hydro-forming the pre-formed tubular member  70  to form a finished tubular member, which in the embodiment illustrated, is the fuel filler neck  36  and manifold connector  38 . As illustrated in  FIG. 3 , the pre-formed tubular member  70  is placed in a die set comprised of an upper die half  72  and a lower die half  74 . The upper die half  72  includes a first stage tubular forming cavity portion  76 . Likewise, the lower die half  74  includes a first stage tubular forming cavity portion  78 . The upper die half  72  includes a second stage tubular forming cavity portion  80 . Likewise, the lower die half  74  includes a second stage tubular forming cavity portion  82 . It should be appreciated that a combined cross-sectional circumferential measure of the first stage tubular forming cavity portions  76  and  78  total up to generally equal to or slightly greater than the cross-section perimeter length of the pre-formed tubular member  70 . 
     In an actual hydro-forming operation, the pre-formed tubular member  70  and a pre-expanded tubular member  84  from the first stage of the die to be described are placed in the tool. The ends of the pre-formed tubular member  70  and the pre-expanded tubular member  84  are sealed. When the ends of the pre-formed tubular member  70  are sealed, hydraulic fluid is pumped into the pre-formed tubular member  70  under pressure. The upper die half  72  and lower die half  74  are closed so that the pre-formed tubular member  70  is progressively deformed and the pressurized fluid captured therein expands the walls of the pre-formed tubular member  70  into the first stage tubular forming cavity portions  76  and  78  of the die. 
     The die halves  72  and  74  are fully closed upon one another with the pre-formed tubular member  70  being tightly clamped between the die halves  72  and  74 . During this closing of the die halves  72  and  74 , a relatively constant hydraulic pressure may be maintained within the pre-formed tubular member  70  by incorporating a pressure relief valve (not shown) into the seal enclosing the ends of the pre-formed tubular member  70  so that hydraulic fluid may be forced from the pre-formed tubular member  70  as it collapses. 
     Once the die is closed, the pre-formed tubular member  70  is then expanded to a cross-sectional profile by increasing the hydraulic pressure sufficient to exceed the yield limit of the tubular member  70  so that the pre-formed tubular member  70  is forced into conformity with the first stage tubular forming cavity portions  76  and  78  of the die halves  72  and  74  to form a pre-expanded tubular member  84 . The die halves  72  and  74  are then opened to permit progressive transfer of the expanded tubular member  84  from the first stage tubular forming cavity  78  into the second stage tubular forming  82 . It should be appreciated that the first tubular forming cavity portions  76  and  78  create all the necessary expansions along the expanded tubular member  84 . It should also be appreciated that, in this step of the method, the expanded round tubular sections are achieved through sectional expansion and some amount of material feeding at the ends of the tubular member. 
     The method also includes the step of moving the expanded tubular member  84  to the second stage tubular forming cavity portions  80  and  82  for final calibration to form a finished tubular member  86 , which in this embodiment, is the fuel filler neck  36  and manifold connector  38  of  FIG. 6 . The method includes the step of positioning the expanded tubular member  84  between the second stage tubular forming cavities  80  and  82 . The upper die half  72  and lower die half  74  are closed so that the expanded tubular member  84  is progressively deformed and the pressurized fluid captured therein expands the walls of the expanded tubular member  84  into the second stage tubular forming cavity portions  80  and  82 . 
     Once the die halves  72  and  74  are closed, the expanded tubular member  84  is then expanded to a cross-sectional profile by increasing the hydraulic pressure sufficient to exceed the yield limit of the expanded tubular member  84  so that the expanded tubular member  84  is forced into conformity with the second stage tubular forming cavity portions  80  and  82  of the die halves  72  and  74 . The die halves  72  and  74  are then opened to permit removal of the finished tubular member  86  from the die halves  72  and  74 . It should be appreciated that the second stage tubular forming cavity portions  80  and  82  create the ribs  62  and ovalize the pre-expanded portions to form the bend and manifold sections  60  and  54 . 
     The finished tubular member  86  may be machined to size and assembled into the fuel filler neck and manifold assembly  34 . It should be appreciated that the die halves  72  and  74  are designed to provide the desired cross-sectional tubular shape. It should also be appreciated that the method is carried out, as illustrated in  FIG. 5 , with the pre-expanded tubular member  84  and finished tubular member  86  being progressively formed with the die halves  72  and  74 . It should further be appreciated that the method can be carried out using one press for the die or two separate presses. 
     The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. 
     Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced other than as specifically described.