Abstract:
In a partition wall arrangement for an exhaust gas pipe section including a partition wall including a main plate member separating the pipe section into two longitudinal passages, a reinforcing plate member is placed over and attached to a major surface of the partition wall member in a part adjacent to the upstream edge of the main plate member so that an improved durability is achieved through elimination of membrane vibrations. By providing an edge cover on the upstream edge of the partition wall, the partition wall can be protected from the adverse influences of the heat from the exhaust gas, and is reinforced even further.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a partition wall arrangement for an exhaust gas pipe for separating the interior of the pipe into a pair of longitudinally extending passages, and in particular to a partition wall arrangement for a pair of exhaust gas pipes which are coupled to each other by a flexible coupling such as a spherical coupling. 
     2. Description of the Related Art 
     An exhaust gas pipe at the converging end of an exhaust manifold for a multi cylinder engine and an exhaust pipe immediately downstream of the exhaust manifold are sometimes each separated into a pair of longitudinal passages each having a semicircular cross section by a corresponding partition wall for the purpose of avoiding exhaust gas interferences. Such a partition wall is exposed to the high temperature of the exhaust gas, and is therefore required to be able to withstand the resulting thermal stress (see Japanese patent laid-open publication No. 9-4451). 
     Also, in order to insulate the vibrations of the engine from being transmitted from the converging end of the exhaust manifold to the exhaust gas pipe in the downstream which is fixedly attached to the vehicle body, a spherical coupling is sometimes interposed between the converging end of the exhaust manifold and the exhaust gas pipe. The engine is typically mounted on rubber mounts to accommodate the vibratory motion of the engine. In such a case, the opposing edges of the partition walls of the converging end of the exhaust manifold and the exhaust gas pipe are spaced from each other so as to accommodate the relative flexing movement of the two parts that are joined by the spherical coupling. Therefore, a small gap is created between the opposing edges of the partition walls. 
     When the edges of the two partition walls oppose each other, and exhaust gas flows along the partition walls at high speed, the partition wall on the downstream side may vibrate as a membrane. This tendency is even more pronounced when the exhaust gas flow contains a pulsating component. This causes a repeated stress to the partition wall, and could severely impair the durability of the partition wall when combined with the effect of the high temperature of the exhaust gas. 
     SUMMARY OF THE INVENTION 
     In view of such problems of the prior art, a primary object of the present invention is to provide a partition wall arrangement for exhaust gas devices having an improved durability through elimination of membrane vibrations. 
     A second object of the present invention is to provide a partition wall arrangement for exhaust gas devices which is relatively free from the adverse influences of the heat of the exhaust gas. 
     A third object of the present invention is to provide a highly durable partition wall arrangement which is easy and economical to manufacture. 
     According to the present invention, such objects can be accomplished by providing a partition wall arrangement for an exhaust gas pipe section including a partition wall separating the pipe section into two longitudinal passages, the partition wall comprising: a main plate member extending diametrically across an inner circumferential surface of the pipe section and longitudinally over a certain length of the pipe section so as to define a pair of longitudinal passages inside the pipe section each having a semi-circular cross section; and a reinforcing plate member placed over and attached to a major surface of the partition wall member preferentially in a part adjacent to the upstream edge of the main plate member. 
     The reinforcing member is effective in reinforcing the partition wall, and raises the resonant frequency of the partition wall. This prevents the membrane vibration of the partition wall even when the exhaust gas flow contains pulsating components, and improves the durability of the partition wall. Because the reinforcement of the upstream edge of the reinforcing plate member is particularly effective in controlling the vibration, the reinforcing member may include a relatively broad upstream portion and a relatively narrow downstream portion so as to minimize the increase in the overall weight of the arrangement. For an added reinforcement, a second reinforcing member may be placed over and attached to the other major surface of the partition wall member preferentially over a part adjacent to the upstream edge of the pipe section. 
     Because the upstream edge of the partition wall is most exposed to the influence of the heat of the exhaust gas, it is preferable to provide an edge cover which is wrapped around upstream end edges of the reinforcing member and the main plate member. The edge cover may consist of a flange or an extension of the reinforcing member. Such an edge cover is also beneficial in reinforcing the edge portion of the partition wall, and in controlling the size of the gap between the opposing edges of the partition walls of two pipe sections which are connected to each other. Reducing the size of the gap contributes to the increase in the engine output and reducing the noises due to the interferences of the pressure pulsations between the different cylinders of the engine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is described in the following with reference to the drawings, in which: 
     FIG. 1 is a perspective view of an exhaust device embodying the present invention; 
     FIG. 2 is a longitudinal sectional view of a part of the exhaust device including a flexible joint coupling two pipe sections to each other; 
     FIG. 3 is a longitudinal sectional view taken along a plane perpendicular to the sectional plane of FIG. 2; 
     FIG. 4 is an end view of one of the exhaust pipe sections as seen from the flange end; and 
     FIG. 5 is an exploded longitudinal sectional view of the exhaust pipe section shown in FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a multi cylinder engine  1  for an automobile is provided with an exhaust manifold  2 . The converging end of the exhaust manifold  2  comprises an upstream exhaust pipe section  3 , which is connected to a downstream exhaust pipe section  4  via a spherical coupling  7 . The exhaust manifold  2  includes a plurality of branch pipes  5  which not only conduct exhaust gas from respective cylinders to the converging end but also mechanically secures the manifold  2  to the engine  1 . The downstream exhaust pipe section  4  is attached to a vehicle body part (not shown in the drawing) via a bracket  6 . 
     Referring to FIG. 2, the spherical joint  7  comprises an annular gasket  8  which is tightly fitted on the upstream pipe section  3  and is provided with a spherical sliding surface on its outer surface. The opposing end of the downstream pipe section  4  is provided with a radial flange  9  consisting of a flared section of a pipe member which is welded to the upstream end of the downstream pipe section  4 . A clamp ring  10  is fitted on the upstream pipe section  3  upstream of the gasket  8 . The inner surface of the flange  9  abuts the spherical sliding surface of the annular gasket  8  in a complementary fashion, and the flange  9  and the clamp ring  10  are resiliently pulled toward each other by spring-loaded threaded bolts passed through the flange  9  and the clamp ring  10 . The gasket  8  seals off the interior of the two pipe sections  3  and  4  from the outside, and the spherical sliding surface accommodates a mutual flexing or pivotal movement of the two pipe sections  3  and  4  in all directions. 
     The two pipe sections are provided with partition walls  12  and  13  which separate the corresponding pipe sections into two longitudinal passages each having a semicircular cross section. As shown in FIG. 3, these partition walls  12  and  13  are aligned with each other, and are provided with opposing edges  37  and  38  that are separated from each other with a small gap d so as to accommodate the mutual flexing movement of the two pipe sections  3  and  4 . In particular, the opposing edge  38  of the partition wall  12  of the upstream pipe section  3  is provided with a convex circular arcuate shape while the opposing edge  37  of the partition wall  13  of the downstream pipe section  4  is provided with a concave circular arcuate shape which is substantially complementary to the convex arcuate shape of the other partition wall  12 . This arrangement accommodates the mutual flexing movement of the two pipe sections  3  and  4  while minimizing the gas communication between the two longitudinal passages. 
     The partition wall  13  of the downstream pipe section  4  comprises a main plate member  15  consisting of a simple plate member extending diametrically across the interior of the pipe section  4  and provided with a pair of side flanges  17  and  18  bent along either side edge in mutually opposite directions so as to conform to the opposing inner circumferential surface of the pipe section  4 . These side flanges  17  and  18  abut the opposing surface of the pipe section  4  substantially without any gap, and are fixedly secured to the pipe section  4 , for instance, by spot welding. 
     The partition wall  13  further comprises a pair of reinforcing plate members  20  and  21 . Each reinforcing plate member  20  and  21  comprises a broader upstream portion  27  and  28 , a narrower downstream portion  29  and  30  and a side flange  23  and  25  bent from a side edge extending straight substantially over the entire length of the reinforcing plate member away from the main plate member  15 . The narrower downstream portions  29  and  30  have a width which is slightly greater than half the inner diameter of the pipe section  4  so that they slightly overlap each other as indicated by numeral  24 . The broader upstream portions  27  and  28  have a width which is slightly smaller than the inner diameter of the pipe section  4  so that they overlap each other over a greater width as indicated by numeral  22 . 
     Thus, the side flanges  17 ,  18 ,  23  and  25  are bent away from each other along either side of the partition wall  13 , and abut the inner surface of the main plate member. These side flanges are attached to the pipe section, for instance, by spot welding. The narrower downstream portions  29  and  30  and broader upstream portions  27  and  28  are fixedly attached to the main plate member  15 , for instance by jointly spot welding them together at the overlapping portions  22  and  24 . Thus, the overlapping portions  22  and  24  including the central part of the upstream edge of the downstream partition wall consists of three layers of plate members. 
     The upstream end edge of the main plate member  15  is provided with a slightly recessed central edge  33 , and a pair of shoulders  36   a  and  36   b  on either side thereof. The upstream edge of one of the reinforcing plate members  20  is provided with an end flange  32  which is bent over the recessed central edge  33  of the main plate member  15  and the end edge of the other reinforcing plate member  21  which is also somewhat recessed from the corresponding end edge of the one reinforcing plate member  20 . The end flange  32  therefore serves as an edge cover that protects the edge of the partition wall  13  from the influences of the heat of the exhaust gas. The outer profile of the end flange  32  after being bent presents an outer end surface  35  which defines the circular arcuate edge  37  of the partition wall  13  jointly with the shoulders  36   a  and  36   b . These edges as well as the flange are all provided with a corresponding concave circular arcuate shape. Thus, in the assembled state of the partition wall  13 , the opposing edges  37  and  38  of the upstream and downstream partition walls  12  and  13  are provided with complementary circular arcuate shapes which are separated by the uniform gap d over the entire width. 
     The end flange  32  wraps around the corresponding edges of the main plate member  15  and the other reinforcing member  21 , and protect them from the heat of the exhaust gas, and increases the rigidity of the upstream edge of the partition wall  13 . More importantly, the reinforcing members  20  and  21  and the end flange  32  jointly reinforce (or increase the rigidity of) the upstream edge of the partition wall, and this can effectively prevent the undesired vibration of the partition wall  13 . 
     It is preferable to provide the end flange  32  in the upper one of the partition wall members  20  and bend it downward to avoid accumulation of residual substances at the edge of the end flange. Also, the reinforcing plate member  20  provided with the end flange  32  may be provided with a smaller thickness than the other reinforcing plate member  21  or may be made of a different material to simplify the work of bending the end flange  32 . In the foregoing embodiment, each reinforcing member included a narrow section  29  and  30  and a broad section  27  and  28  so as to define the shape of letter-L, but may also be provided with other tapering shapes such as a triangle. 
     Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims.