Abstract:
The invention relates to a tubular structure ( 1 ) that can form part of a motor vehicle axle, comprising at least one first tubular élément ( 15 ), at least one second tubular élément ( 16 ) and a Connecting piece ( 61, 62 ) fixing the first and second tubular éléments ( 15, 16 ) by welding, such that the Connecting piece ( 61, 62 ) is welded to one ( 15 ) of the two tubular éléments ( 15, 16 ) by at least one weld bead extending along a line forming said tubular élément ( 15 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National stage, under 35 U.S.C. §371, of International App. No. PCT/FR2010/051892 which was filed on Sep. 10, 2010 and claims priority to French Application No. 0956275 which was filed on Sep. 11, 2009, and which is incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND 
       [0003]    This invention relates to a tubular structure having a link between two tubular members. More specifically, a tubular structure includes a first tubular member, a second tubular member, and a connector interconnecting the two tubular members, such as by welding. 
         [0004]    U.S. Pat. No. 4,660,345 discloses a tubular assembly with a connector assembled by welding a pair of tubular members. In particular, in  FIG. 24  welding seams are visible on the tubular assembly. The welding seams are generally positioned along radial lines across the surface of the tubular members to be assembled. During welding, heat is created along these seams and creates a radial expansion of the tube. During cooling, the effects of the expansion may leave the tube with a residual curvature. This residual curvature is difficult to model because it is dependent on the molecular structure of the tube, which is rarely homogeneous. This risk is even more critical when the weld seams do not run over the entire peripheral surface of the tubes, which can cause expansion of one portion of the tube and no expansion of the other portion, thereby creating residual stresses at the intersection of the two portions. 
         [0005]    One aspect of the present invention includes an assembly having two tubular members secured by welding a connector that prevents the appearance of curvatures during assembly of the tubular members. For this purpose, the invention has a tubular structure, such as a portion of a vehicle axle, including at least one first tubular member, at least one second tubular member, and a connector interconnecting the first and second tubular members by welding. The connector welds onto one of the two tubular members with at least one welding bead that extends along a generating line of the tubular member. The end of the second tubular member seats against the first tubular member, with the axis of the end of the second tubular member generally in the same plane as the axis of the first tubular member. 
         [0006]    In one embodiment, the connector welds onto the two tubular members with at least one welding bead extending along one of the generating lines of each of the two tubular members, with the ends of the two tubular members having a generally circular cross-section. 
         [0007]    Thus, the connector securing the two tubular members includes a first welded portion on the second connecting member and a second welded portion on the first connecting member. The first portion of the connector includes a generally V-shaped or U-shaped section, with the ends defining the contact lines between the connector and the end of the second tubular member. The welding seams are carried out along these contact lines. The spacing between the ends are preferably less than or equal to the outside diameter of the circular end of the second tubular member. The second portion of the connector is generally planar, with the end portion having a straight edge that defines a rectilinear contact line between the connector and the first tubular member. The welding seam is produced along this contact line. The connector includes an indexing hole that allows positioning of the connector in relation to a reference point on the first tubular member during assembly by welding the connector on the first tubular member. 
         [0008]    In another embodiment, the connector includes two half-shells positioned diametrically on opposite sides of the second tubular member, so that the straight edges of the second portions of the two half-shells sandwich the first tubular member. The second tubular member also includes an indexing hole that allows positioning of the second tubular member in relation to a reference point on the first tubular member or in relation to one indexing hole of one of the two half-shells. 
         [0009]    The invention also includes a method of assembling a tubular structure assembly having the above characteristics, including:
       a first step of positioning the second portions of the two half-shells diametrically on either side of the first tubular member by a tool pre-positioning itself relative to one reference point belonging to the first tubular member, the tool including two guide pins inserting into the indexing holes of the half-shells,   a second step of welding the weld seams along to the contact lines of the two half-shells on the first tubular member, said contact lines extending along generating lines of the first tubular member;   a third step of positioning the end of the second tubular member between the first portion of the two half-shells relative to one point of reference belonging to the first tubular member or relative to an indexing hole of one of the half-shells, by using a tool including a finger inserting into the indexing hole of the second tubular member;   a fourth step of clamping the two half-shells against the second tubular member; and       
 
         [0014]    a fifth step of welding the two half-shells on the second tubular member, along the contact lines of the two half-shells, the contact lines extending along the generating lines of the second tubular member. 
         [0015]    The invention also relates to an axle of a vehicle wheel having a central portion formed by a tubular structure including at least one of the preceding characteristics. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0016]    Other advantages and technical characteristics of this invention will become more apparent in light of the following description with reference to the accompanying drawings in which: 
           [0017]      FIG. 1  is a partial perspective view of a rear axle of a vehicle having an axle according to the present invention; 
           [0018]      FIG. 2  is a perspective view of the axle according to the present invention; and 
           [0019]      FIGS. 3 and 4  are detailed views of the axle. 
       
    
    
       [0020]    Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. 
       DETAILED DESCRIPTION 
       [0021]      FIG. 1  is a partial perspective view of a rear axle of a vehicle. This rear axle includes an axle  1 , fixed to the structure of the vehicle (not shown) via several attachment assemblies  2 . The attachment assemblies  2  include an attachment screw positioned in viscoelastic wedges. The rear axle  1  supports different assemblies of suspension arms  3  positioned symmetrically on both sides of this axle  1 . Each assembly of suspension arms  3  supports a hub  4  on which a wheel can be attached (not shown). Five sets of damper spring assemblies  5  are positioned on both sides of the axle  1 , having a first end secured to the axle  1  and a second end secured to each hub  4 . 
         [0022]      FIGS. 2 to 4  illustrate a perspective view of axle  1  and a detailed view of the axle  1 . The axle  1  includes two lateral portions  11  positioned symmetrically on either sides of a central portion  12  which comprises a tubular assembly. Each of the two lateral portions  11  are formed by stamped sheet metal presenting shapes adapted for installation of the attachment assemblies  2  and the suspension arms  3  ( FIG. 1 ). The central portion  12 , of the “mechanical welded” type, includes a first tubular frame  13  and a second tubular frame  14 , with the second tubular frame  14  generally aligned above the first tubular frame  13 . Each of these two tubular frames  13  and  14  are formed of two tubes  15 , generally aligned longitudinally with the vehicle, and two tubes  16  aligned generally transversely with the vehicle. The ends of the traverse tubes  16  are connected to the end of one of the longitudinal tubes  15  with a connector  6 . 
         [0023]    The transverse tubes  16  include a cylindrical portion at each end for attachment of the connector  6  and a central portion, which is not necessarily straight, where any curvatures allow adaption to the environment in which the axle  1  is positioned. The transverse tubes  16  include an indexing hole  17  for positioning during assembly of the axle  1 , as explained below. 
         [0024]    The longitudinal tubes  15  have a generally cylindrical shape of a constant diameter, for force-fitting into cylindrical openings positioned in the lateral portions  11 , interconnecting the two lateral portions  11  to the tubular central portion  12 , and forming the axle  1 . 
         [0025]    The connector  6  is formed from an upper half-shell  61  and of a lower half shell  62 , positioned against one another, coming to frame each of the connections between the transverse tubes  16  and the longitudinal tubes  15 . The lower  61  and upper  62  half-shells can either be identical, or contain differences of geometry, for example, where the axes of the ends of the longitudinal tubes and the transverse tubes  16  are not in a same plane. The lower  61  or upper  62  half-shells include a first portion  64  of a constant cross-section with a transverse section being generally V-shaped or U-shaped, the U-shape preferably being flared. The two arms  65  form an open angle. An indexing hole  63  is defined between these two arms  65 , which will be explained further below. This first portion  64  is extended by a second portion  67  progressively flattening until forming a straight section whose end edge is positioned generally perpendicularly to the two parallel edges of the two arms  65 . The far side of the second portion  67  acts as contact surface between the half-shells  61  or  62  and the longitudinal tubes  15 . 
         [0026]    Advantageously for the assembly of the axle  1 , the two lateral portions  11 , formed by several members made of sheet metal, are assembled on a frame forming a welding template. The geometry of these two lateral portions  11  depends on the final geometry of the axle  1 . 
         [0027]    The two longitudinal tubes  15  are assembled on each of the two lateral portions  11 , which support the transverse tubes  16  and form the lower  13  and upper  14  frameworks. The longitudinal tubes  15  are force-fitted into circular openings defined in the lateral portions  11  and secured by welding seams. Thus, the welding seams run over the intersection between the sides of the circular openings of the lateral portions  11  and the peripheral surface of the longitudinal tubes  15 . This creates an axial expansion of the longitudinal tubes  15  that no longer guarantees the axial geometry of the longitudinal tubes  15  after cooling. 
         [0028]    Once the longitudinal tubes  15  are secured, the lower  61  and upper  62  half-shells are assembled by welding close to the ends of these longitudinal tubes  15 . The lower  61  and upper  62  half-shells are positioned on both sides of the longitudinal tubes  15 , sandwiching them symmetrically, and following two diametrically opposite positions. The lower  61  and upper  62  half-shells are pre-positioned by a tool (not shown) at during welding. The pre-positioning tool includes positioning pins for insertion into the indexing hole  63  of the lower  61  and upper  62  half-shells, for positioning of the half-shells  61  and  62  relative to the lateral portions  11 . As discussed above, this positioning cannot be done relative to the longitudinal tubes  15  because the axial geometry is no longer reliable. Welding seams are formed along the contact lines between the end edges of the second portions  67  of the lower  61  and upper  62  half-shells, and the lateral surfaces of the longitudinal tubes  15 . Welding is performed along the generating lines of the longitudinal tubes  15 , to limit the expansion effects of the tubes, so that positioning of the lower  61  and upper  62  half-shells relative to the lateral portions  11  is maintained after the welding has cooled. 
         [0029]    Once the lower  61  and upper  62  half-shells are fixed symmetrically close to each end of the longitudinal tubes  15 , they form the supports to position the cylindrical ends of the transverse tubes  16 . The indexing holes  17  of the longitudinal tubes  16  maintain their positions at the time that the lower  61  and upper  62  half-shells are clamped around the cylindrical ends of these longitudinal tubes  16 . The lower  61  and upper  62  half-shells, which provide a certain flexibility of positioning, can easily adapt to different diameters of tubes. This allows a pre-positioning during welding along the contacts lines between the lower  61  and upper  62  half-shells and the peripheral surfaces of the ends of the transverse tubes  16 . As previously noted, the welding itself is done along generating lines of the ends of the transverse tubes  16 , the distortion according to the axial alignment of the ends of these transverse tubes  16  from this fact are negligible. Once the welds are cooled, the geometry and the positioning of the transverse tubes  16  are maintained, guaranteeing the final geometry of the axle  1  is formed. 
         [0030]    Each upper  61  or lower half shell  62  provides the advantage of being formed from a single metal plate, with a large enough tolerance in the variation of the angle formed between the arms  65  of the V or of the U. The diameter of the cylindrical ends of the transverse tubes  16 , while remaining at a reasonable size range, can vary. To permit the welding seams to form along the contact lines between the sides of the arms  65  of the first portions  64  of the lower  61  and upper  62  half-shells and the lateral surfaces of the ends of the transverse tubes  16 , following generating lines of these tubes, the outside diameter of these transverse tubes  16  must remain greater than the deviation of the two parallel sides of the two arms  65  of the upper  61  or lower  62  half-shells. 
         [0031]    It is also possible to modify, to a certain extent, while keeping some transversal tubes  16  identical the spacing between the longitudinal tubes  15  and the transverse tubes  16 , by modifying the width of the axle  1 . Such a spacing is possible because it is not necessary for the transverse tubes  16  to contact the longitudinal tubes  15  for assembly. Therefore, the spacing may vary without weakening the installation. 
         [0032]    The axle  1  formed with the tubular assembly provides a significant free interior volume, delimited by the two lateral portions  11  and the two frames  13  and  14 , permitting the installation of a rear differential in the case, for example, of a four wheel drive type vehicle or of an electric motor for an application to a hybrid or electric vehicle. 
         [0033]    It is well understood that the invention is not limited to embodiments described herein, but enables one skilled in the art to make numerous modifications. 
         [0034]    Changes can be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.