Abstract:
An exhaust volume for combustion gases from a motor vehicle engine comprises at least one exhaust duct delimited by a wall comprising an end segment, and at least one flange having a bearing surface. The flange delimits at least one exhaust gas inlet communicating with the exhaust duct. The exhaust gas inlet is delimited by a cannon connected to the flange, with the cannon being attached to the end segment. At least one outer neck is attached to the end segment. The end segment is arranged between the flange and the outer neck, with the end segment being pierced with at least one hole between the flange and the outer neck. The end segment, the flange, and the outer neck are being secured through the addition of a filler.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to FR application No. 12 50403, filed Jan. 16, 2012. 
       TECHNICAL FIELD 
       [0002]    The present invention generally relates to exhaust volumes for motor vehicles. 
         [0003]    More specifically, according to a first aspect, the invention relates to an exhaust volume comprising at least one exhaust duct delimited by a wall comprising an end segment; and at least one flange having a bearing surface. The flange delimits at least one exhaust gas inlet communicating with the exhaust duct, and the exhaust gas inlet is delimited by a cannon connected to the flange, with the cannon being attached to the end segment. 
       BACKGROUND OF THE INVENTION 
       [0004]    Such an exhaust volume is known from the patent application filed under no. FR 11 59216. This application describes an exhaust manifold in which waves can be arranged easily. The manifold described in that application comprises an exhaust duct and a flange, the flange including a cannon made up of a first segment extended by a second segment that is not as thick as the first segment, and is connected to the wall of the exhaust duct. The second segment of the flange and the wall of the exhaust duct are typically secured to one another by brazing. The wall of the exhaust duct covers the second segment over the entire height of said second segment. Due to the large size of the overlap, brazing allows a particularly strong connection of the first and second cannons to one another. However, patent application no. FR 11 59216 does not describe how to connect the duct to the cannon when the cannon is enclosed in a double cooling jacket, or more generally an outer neck. 
       SUMMARY OF THE INVENTION 
       [0005]    An exhaust volume as described below makes it possible to resolve the aforementioned problem. 
         [0006]    The exhaust volume for the combustion gases from a motor vehicle engine of the aforementioned type comprises at least one outer neck attached to the end segment. The end segment is arranged between the flange and the outer neck. The end segment is pierced with at least one hole between the flange and the outer neck The end segment, the flange, and the outer neck are secured through the addition of a filler. 
         [0007]    In this way, it is possible to obtain a solid and strong connection between the cannon, the outer neck, and the duct. In fact, the filler metal first infiltrates an inner side of the duct, in an interstice located between the duct and the cannon; it then infiltrates the hole, then an outer side of the duct, in an interstice located between the duct and the outer neck. In this way, the hole allows easy passage from the inner side to the outer side, between the two interstices. It is thus easier to secure the flange, the end segment, and the outer neck. 
         [0008]    The exhaust volume is for example an exhaust manifold. 
         [0009]    Alternatively, the exhaust volume is a member for purifying exhaust gases, or a muffler. 
         [0010]    Typically, the exhaust volume is an element of the hot part of the exhaust line. 
         [0011]    Advantageously, the hole is formed in the end segment of the wall of the exhaust duct. For example, the hole is cylindrical and has an oval or oblong section. The section, for example, has a diameter several millimeters long. 
         [0012]    Alternatively, several holes are distributed around the end segment. 
         [0013]    The flange is typically shared by all of the exhaust gas inlets, as described in patent application no. FR 11 59216. It thus delimits a plurality of exhaust gas inlets, at least one for each exhaust gas outlet of the engine block. 
         [0014]    Alternatively, the exhaust volume has several flanges, for example one for each exhaust gas outlet of the engine block. 
         [0015]    In all cases, each flange is a plate with a small thickness, made from a metal material. This material is typically stainless steel, for example austenitic steel. Each flange has a thickness between 1 and 4 mm, for example 2.5 mm. 
         [0016]    Each flange is typically pressed by its bearing surface against the engine block, directly or with an inserted seal. Each exhaust gas inlet is placed across from an exhaust gas outlet formed in the engine block, through which the gases coming from the various combustion chambers of the engine escape. 
         [0017]    Alternatively, each flange may be pressed against another element of the exhaust circuit. 
         [0018]    The cannon is formed in the flange, in that the cannon is integral with the flange. Alternatively, the cannon may be connected to the flange by a connector. The cannon, for example, has a generally cylindrical shape, typically with a circular section. 
         [0019]    The flange includes a substantially planar portion, for example pressed against the engine block, in which the inlet is pierced. The cannon protrudes relative to the planar portion, from a side of the planar portion opposite the engine block or the element of the exhaust circuit. The cannon has a central axis substantially perpendicular to the planar portion of the flange. 
         [0020]    The filler is typically added by brazing. 
         [0021]    The wall of the exhaust duct has an end segment. The end segment is, for example, integral with the wall of the exhaust duct. Alternatively, the end segment may be connected to the wall of the exhaust duct by a connector. 
         [0022]    The end segment preferably has a flared end. The concave portion of the flared end is arranged on the side opposite the exhaust duct, the convex portion being turned toward the inside of the exhaust duct. 
         [0023]    The outer neck bears on the flared end of the end segment. More specifically, the outer neck rests on the concave portion of the flared end. 
         [0024]    Furthermore, the cannon includes a first segment extended by a second segment with a smaller thickness than the first segment, the cannon having a shoulder between the first and second segments, the flared end bearing on the shoulder. 
         [0025]    The thickness of the second segment is, for example, comprised between 0.5 mm and 3 mm, and is preferably equal to 1.25 mm. 
         [0026]    In this way, the outer neck rests on the flared end of the wall of the exhaust duct, with the flared end in turn resting on the shoulder of the flange. In this way, proper positioning of the parts is ensured. Furthermore, this feature allows an allowance over the total length of the exhaust volume. 
         [0027]    Furthermore, the first segment is inserted between the second segment and the planar portion. The second segment is arranged toward the exhaust duct relative to the first segment. 
         [0028]    Furthermore, due to the smaller thickness of the second segment, the heating necessary to infiltrate the filler metal is reduced, such that the risk of deforming the bearing surface of the flange during that step is reduced. It is very important to preserve the flatness of the bearing surface to allow proper fastening of the flange. 
         [0029]    The end segment, the second segment, and the outer neck advantageously have substantially the same thickness. Thus, the heating due to the brazing does not cause an interstice between the different parts of the exhaust volume. 
         [0030]    The radial spacing between the end segment and the outer neck is smaller than 0.2 mm. Furthermore, the radial spacing between the end segment and the second segment is comprised between 0.05 mm and 0.45 mm. “Radial spacing” refers to the radial distance separating the outer neck from the end segment on the one hand, and the radial distance separating the second segment from the flange and the end segment on the other hand. These small radial spacing values allow better strength of the exhaust volume, and better sealing. This is particularly important when the outer neck is part of a double circulation enclosure for a cooling fluid. This in particular results from the fact that these three parts—outer neck, cannon, duct—have substantially the same thickness. The fact that the cannon has a second segment with a smaller thickness is advantageous in this context, since the heating necessary to infiltrate the filler metal is reduced. 
         [0031]    As described above, the outer neck and the flange form a double enclosure delimiting a space provided for the circulation of the coolant liquid. 
         [0032]    The double enclosure includes an outer wall substantially parallel to the flange and an outer neck for each duct, which is upright relative to the outer wall. The outer neck is placed around the corresponding duct. The outer neck is coaxial to the exhaust duct. 
         [0033]    The cooling liquid is, for example, water or air. 
         [0034]    The securing by brazing as previously described then prevents any leakage of the cooling liquid, and gives the exhaust volume excellent sealing. 
         [0035]    According to a second aspect, a method for manufacturing an exhaust manifold having the aforementioned characteristics includes the following steps: deforming the outer neck; piercing a hole in the end segment; positioning the inlet of the exhaust duct across from the flange; and securing the flange, the end segment, and the outer neck by adding a filler. 
         [0036]    According to this technique, the outer neck is deposited against a die with a hollow shape having rounded edges corresponding to an intermediate shape of the outer neck to be produced. The outer neck is deformed using a punch. The punch is pressed against the rounded edge of the die, at the inlet of the hollow portion. The punch is inserted into the hollow portion of the die and therefore makes it possible to give the neck its intermediate shape. Under the effect of the pressure applied by the punch, the outer neck deforms and bends. In this way, the outer neck adopts a substantially rounded shape, the edge of the die being inclined by approximately 45° relative to the horizontal plane. 
         [0037]    The flange is formed according to the flange formation step described in patent application no. FR 11 59216. 
         [0038]    The end segment of the wall of the exhaust duct is then pierced. This step is carried out using a die and a punch with different shapes from the die and the punch used in the steps for deforming the outer neck. The die has substantially the same diameter as the exhaust duct. The die is inserted inside the exhaust duct, at the end segment. A punch is then placed outside the wall of the exhaust duct, at the end segment, across from the die. Under the effect of the pressure exerted on the punch, the end segment is pierced and then forms a hole. 
         [0039]    The inlet of the exhaust duct is positioned across from the flange. In this way, the flared end of the wall of the exhaust duct is across from the shoulder of the flange such that the flared end can rest on the flange. 
         [0040]    The flange, the end segment, and the outer neck are secured by adding a filler. A heating mechanism is arranged inside the exhaust duct, at the end segment of the wall of the exhaust duct. The filler material is brought to the inlet of the interstice situated between the flange and the end segment. Under the effect of the heat, the filler melts and infiltrates the interstice. 
         [0041]    Thus, the filler is first inserted between the flange and the end segment, then into the hole, then between the end segment and the outer neck. 
         [0042]    The method may also include the following steps: forming the flared end; and pre-positioning the flared end on the outer neck. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    Other features and advantages of the invention will emerge from the following detailed description provided below, for information and non-limitingly, in reference to the appended Figures, in which: 
           [0044]      FIG. 1  is an axial cross-sectional view of the exhaust volume according to the invention; 
           [0045]      FIG. 2  is an enlarged cross-sectional view of part of the exhaust volume of  FIG. 1 ; 
           [0046]      FIG. 3  is a diagrammatic illustration of the step for deforming the outer neck; 
           [0047]      FIG. 4  is a diagrammatic illustration of the steps for piercing the hole in the end segment; 
           [0048]      FIG. 5  is a diagrammatic illustration of the step for pre-positioning the flared end on the outer neck; 
           [0049]      FIG. 6  is a diagrammatic illustration of the step for forming the flared end; 
           [0050]      FIG. 7  is a diagrammatic illustration of the step for positioning the inlet of the exhaust duct across from the flange; 
           [0051]      FIG. 8  is a diagrammatic illustration showing the steps for securing the flange, the end segment and the outer neck. 
       
    
    
     DETAILED DESCRIPTION 
       [0052]    The manifold  1  shown in  FIG. 1  is provided to collect the exhaust gases coming from the outlets of the combustion chambers of the engine  5 , also called the engine block. The manifold  1  comprises: a plurality of exhaust ducts  2 ; a flange  3  having a bearing surface  4  provided to be pressed against the engine  5 , the flange delimiting a plurality of exhaust gas inlets  6 ; a plurality of outer necks  7 ; and an exhaust gas outlet (not shown) in communication with the exhaust ducts  2 . 
         [0053]    The exhaust ducts  2  guide the exhaust gases from the inlets  6  to the outlet. They each include a tubular wall  9 . The tubular wall  9  delimits a circulation passage for the exhaust gases from the inlets  6  to the outlet. 
         [0054]    The upstream portions of the ducts  2  are substantially rectilinear, and perpendicular to the bearing surface  4  of the flange. The ducts  2  extend around the longitudinal axis X shown in  FIG. 1 . The axis X is substantially perpendicular to the bearing surface  4 . 
         [0055]    The wall  9  is made from stainless steel, for example austenitic steel. 
         [0056]    The flange  3  is a planar plate, made from stainless steel, for example austenitic steel. The inlets  6  are formed in the flange  3 . 
         [0057]    The flange  3  is arranged such that the inlets  6  are placed to coincide with the exhaust gas outlets. 
         [0058]    As shown in  FIG. 2 , each inlet  6  is delimited by a cannon  10  formed in the flange  3 . The cannon  10  protrudes relative to the flange  3  toward the duct  2 , i.e. opposite the bearing surface  4 . Furthermore, the duct  2  has an inlet opening  12 , the wall  9  having an end segment  11  delimiting the inlet opening  12 . The inlet opening  12  is positioned across from the corresponding exhaust gas inlet  6 . 
         [0059]    The end segment  11  has a diameter slightly larger than the diameter of the duct  2 . In this way, the wall  9  and the cannon  10  are in the extension of one another. This difference in diameter reveals an outer shoulder  31 . 
         [0060]    Each end segment  11  cooperates with the cannon  10  of the corresponding inlet to delimit a sealed passage for the exhaust gases from the inlet  6  to the corresponding inlet opening  12 . 
         [0061]    As illustrated in  FIG. 2 , the end segment  11  has a wall thickness substantially equal to the thickness of the wall  9 . Considered in cross-section perpendicular to the central axis X of the inlet  6 , the segment  11  has a substantially circular section. 
         [0062]    The end segment  11  has a flared end  16 . The concave portion of the flared end  16  is arranged on the side opposite the duct  2 , the convex portion being turned toward the inside of said duct  2 . 
         [0063]    As shown in  FIG. 2 , the outer neck  7  is positioned bearing on the flared end  16  of the end segment  11 . 
         [0064]    Furthermore, the end segment has a hole  23  situated between the outer neck  7  and the flange  3 . 
         [0065]    Furthermore, the cannon  10  comprises a first segment  13  with a larger thickness toward the flange  3 , extended by a second segment  14  having a smaller thickness toward the duct  2 . 
         [0066]    The first segment  13  has substantially the same thickness as the flange  3 . 
         [0067]    The second segment  14  has a thickness substantially corresponding to the thickness of the wall  9 . 
         [0068]    The first and second segments  13  and  14  are connected to one another by a shoulder  15 . The shoulder  15  delimits an annular surface, substantially perpendicular to the longitudinal axis X of the inlet  6 . 
         [0069]    In this way, the outer neck  7  rests on the flared end  16  of the wall of the duct  2 , with the flared end  16  in turn resting on the shoulder  15  of the flange  3 . 
         [0070]    The method for manufacturing the exhaust volume described above will now be explained, in reference to  FIGS. 3 ,  4 ,  5 ,  6 ,  7  and  8 . 
         [0071]    The method comprises the following steps: deforming the outer neck; piercing a hole in the end segment; positioning the inlet of the exhaust duct across from the flange; and securing the flange, the end segment, and the outer neck by adding a filler. 
         [0072]    The step for deforming the outer neck  7  is illustrated in  FIG. 3 . 
         [0073]    This step is carried out by punching using a die  17  and a punch  19 . The die  17  has a hollow shape and has rounded edges  18 . The punch  19  has a substantially tapered portion  20 . The neck is positioned on the rounded edge  18  of the die  17 . The punch  19  is pressed at the inlet of the hollow portion against the rounded edge  18  of the die  17 , then is inserted into the hollow portion of the die  17  and makes it possible to give the neck an intermediate shape. Under the effect of the pressure applied by the punch  19 , the outer neck  7  deforms and folds to reach its intermediate shape. 
         [0074]      FIG. 4  illustrates the step for piercing a hole in the end segment. 
         [0075]    This step is carried out using a die  21  and a punch  22  with shapes different from the die  17  and the punch  19  used in the step for deforming the outer neck  7 . 
         [0076]    The die  21  has substantially the same diameter as the duct  2 . The die  21  is inserted inside the duct  2 , at the end segment  11 . 
         [0077]    The punch  22  is positioned outside the duct  2 , in contact with the outer side of the wall. The punch  22  is placed at the height of the end segment  11 , across from the die  21 . 
         [0078]    Pressure is exerted radially on the punch  22  toward the inside of the duct  2 . Under the effect of that pressure, the end segment  11  is pierced and forms the hole  23 . 
         [0079]    The method includes a step for pre-positioning the flared end  16  on the outer neck  7 . This step is shown in  FIG. 5 . The outer neck  7  is positioned against the wall  9 , at the end segment  11 , across from the hole  23 . 
         [0080]    The method also includes a step for forming the flared end illustrated in  FIG. 6 . 
         [0081]    This step is also carried out with a die  27  cooperating with a punch  28 . 
         [0082]    The die  27  has an opening  29 . The die  27  also comprises rounded edges  30  designed to give the outer neck  7  its final shape. 
         [0083]    The punch  28  has an irregular diameter. The head of the punch  28  has a diameter corresponding to the diameter of the duct  2 . The shape of the remaining portion of the punch is conjugated with the shape of the and segment  11  and the flared end  16 . 
         [0084]    The outer neck  7  and the end segment  11  deform under the effect of the pressure applied by the punch. The outer neck  7  adopts a rounded shape, the edge of the die being inclined at approximately 90° relative to the horizontal plane. The end segment  11  adopts its final shape revealing the bend of the flared end  16 . 
         [0085]      FIG. 7  illustrates the steps for positioning the inlet of the duct  2  across from the flange  3 . 
         [0086]    The positioning of the duct  2  across from the flange  3  is done such that the flared end  16  faces the shoulder  15  such that said flared end  16  can rest on said shoulder  15 . 
         [0087]    Furthermore, the duct  2  and the flange  3  are positioned such that the hole  23  is situated between the second segment  14  and the outer neck  7 . 
         [0088]    The step for securing the flange  3 , the end segment  11 , and the outer neck  7  is shown in  FIG. 8 . This step may for example be carried out under a protective gas. 
         [0089]    A heating mechanism  24  is arranged inside the duct  2 , at the end segment  11 . The filler material  25  is brought to the inlet of the interstice  26  situated between the second segment  14  and the end segment  11 . The filler material  25  is housed on an inner side of the duct  2 , against the shoulder  31  situated between the inlet opening  12  and the wall  9 . The filler material  25 , for example, assumes the form of a solid ring. Under the effect of the heat, the filler material  25  melts and infiltrates the interstice  26 . The filler material  25  infiltrates between the flange  3  and the end segment  11 , in the hole  23 , then between the end segment  11  and the outer neck  7 . 
         [0090]    Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.