Abstract:
An extension portion extending outwardly is integrally formed on the edge of an end portion of an exhaust pipe; a collar is fixed on the outer periphery of the end portion of the exhaust pipe by caulking; and the edge of the outer end of the collar is abutted against the extension portion. The aforementioned arrangement provides a connection portion of an exhaust pipe for an engine which is intended to rigidly connect the exhaust pipe to an exhaust port of the engine, to prevent gas leakage by eliminating the occurrence of clearance at the connecting portion, to reduce the flow resistance of exhaust gas in the exhaust pipe, and to reduce the production cost of the connection portion.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a structure of a connection portion of an exhaust pipe, where the connection portion is connected to an exhaust port of an engine, typically, an engine for a motorcycle.  
         BACKGROUND ART  
         [0003]    An example of a connection portion of an exhaust pipe, where the connection portion is connected to an exhaust port of an engine is disclosed in Japanese Patent Utility Model Laid open No. Sho 61 88021.  
           [0004]    The above described related art structure is configured such that a collar is fitted to the outer periphery of an end portion of the exhaust pipe, and the inner peripheral surface of the collar is fixed to the edge of an end portion of the exhaust pipe by welding; and the exhaust pipe is connected to the exhaust port via the collar by means of bolts.  
           [0005]    The above described related art structure, however, has the following problems: (1) Since the exhaust pipe is connected to an exhaust port via the collar by means of bolts, stress concentration may occur at a welding portion between the exhaust pipe and the collar, thereby reducing the strength of the connection portion; (2) a clearance between the exhaust pipe and the collar may become larger due to looseness therebetween and the like, thereby causing gas leakage due to occurrence of cracks or the like; and (3) the welding control for preventing a reduction in flow resistance of exhaust gas flowing in the exhaust pipe due to welding beads formed on welding between the exhaust pipe and the collar is complicated.  
         SUMMARY OF THE INVENTION  
         [0006]    In view of the foregoing, the present invention has been made to solve these problems of the related art, and to improve the overall state of the art.  
           [0007]    An object of the present invention is to provide a new structure of a connection portion of an exhaust pipe for an engine.  
           [0008]    To achieve the above object, there is provided a connection portion of an exhaust pipe, where the connection portion is connectable to an exhaust port side of an engine, the connection portion includes an extension portion extending radially outwardly and integrally formed on an edge of an end portion of the exhaust pipe; and a collar fixed to an outer periphery of the end portion of said exhaust pipe by crimping, wherein the edge of an end portion of said collar is abutted against said extension portion. With this configuration, the exhaust pipe can be rigidly connected to the exhaust port without occurrence of stress concentration therebetween; a clearance between the exhaust pipe and the collar is made as small as possible; since there is no welding bead appeared in the related art structure of a connection portion of an exhaust pipe, the flow resistance of exhaust gas is not increased, and therefore, it is not required to perform mechanical treatment for reducing the flow resistance of exhaust gas; and since the welding means is not required, it is possible to significantly reduce the cost.  
           [0009]    In addition, to achieve the above object, there is provided a connection portion of an exhaust pipe, where the connection portion is connectable to an exhaust port side of an engine, the connection portion includes a reinforcing outer pipe fixed on an outer periphery of an end portion of the exhaust pipe by crimping; and a collar fixed on an outer periphery of said outer pipe. With this configuration, the reinforcing outer pipe can be rigidly fixed to the exhaust pipe without welding, to significantly increase the strength of the connection portion of the exhaust pipe, and also a clearance between the exhaust pipe and the outer pipe is made as small as possible.  
           [0010]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
         [0012]    [0012]FIG. 1 is a side view, with a portion broken away, of an exhaust pipe including a connection portion structure of the present invention (first embodiment);  
         [0013]    [0013]FIG. 2 is a sectional view taken on line  2 - 2  of FIG. 1 (first embodiment);  
         [0014]    [0014]FIG. 3 is a sectional view taken on line  3 - 3  of FIG. 1 (first embodiment);  
         [0015]    FIGS.  4 ( a ) to  4 ( c ) are sectional views showing a process of fixing a collar to an exhaust pipe by crimping (first embodiment);  
         [0016]    [0016]FIG. 5 is a sectional view showing a state in which the exhaust pipe is assembled in an engine (first embodiment);  
         [0017]    [0017]FIG. 6 is a side view, with a portion broken away taken along line  6 - 6  of FIG. 7, showing an exhaust pipe including a connection device of the present invention (second embodiment);  
         [0018]    [0018]FIG. 7 is a sectional view taken on line  7 - 7  of FIG. 6 (second embodiment);  
         [0019]    [0019]FIG. 8 is a sectional view showing a state in which the exhaust pipe is assembled in the engine (second embodiment); and  
         [0020]    [0020]FIG. 9 is a sectional view showing a state in which an exhaust pipe in the engine (third embodiment). 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    First, a first embodiment of the present invention will be described with reference to FIGS.  1  to  5 .  
         [0022]    [0022]FIG. 1 is a side view, with a portion broken away taken on line  1 - 1  of FIG. 3, showing an exhaust pipe including a connection portion structure of the present invention;  
         [0023]    [0023]FIG. 2 is a sectional view taken on line  2 - 2  of FIG. 1; FIG. 3 is a sectional view taken on line  3 - 3  of FIG. 1; FIGS.  4 ( a ) to  4 ( c ) are sectional views showing a process of fixing a collar to an exhaust pipe by crimping; and FIG. 5 is a sectional view showing a state in which the exhaust pipe is assembled in an engine.  
         [0024]    Referring to FIGS.  1  to  3 , a flange like extension portion  1   a  projecting radially outwardly is integrally formed on the edge of a connection side end portion, to be connected to an exhaust port Pe of an engine E (see FIGS. 5, 8 &amp;  9 ), of a stainless steel made cylindrical exhaust pipe  1 . The base end of the extension portion  1   a  is formed into a rounded plane.  
         [0025]    A carbon steel short sized cylindrical collar  2  is rigidly fixed, by a crimp Ck, on the outer periphery of a connection side end portion, to be connected to the exhaust pipe Pe of the engine E, of the exhaust pipe  1  by means of a crimping means to be described later. The edge of the outer end of the collar  2  abuts against the inner end surface of the extension portion  1   a.    
         [0026]    A carbon steel rhombic joint  3  is slidably fitted on the outer periphery of the end portion of the exhaust pipe  1  at a position offset inwardly from the collar  2 . One end surface of the joint  3  is abutted against the inner end surface of the collar  2 . The joint  3  is used for connecting the exhaust pipe  1  to the opening end of the exhaust port Pe of the engine E in co-operation with stud bolts  4  (see FIGS. 5, 8 &amp;  9 ) planted by screwing in the surface portion of the opening end of the exhaust port Pe of the engine E. A pair of bolt holes  5  for allowing the stud bolts  4  to pass therethrough are provided in the outer end portion, opposed to the opening end of the exhaust port Pe, of the joint  3 .  
         [0027]    Referring to FIGS.  4 ( a ) to  4 ( c ), a process of fixing the collar  2  to the end portion of the exhaust pipe  1  by crimping is shown. The entire outer periphery of the collar  2  is crimped from outside to the outer periphery of the exhaust pipe  1 . As shown in FIG. 4( a ), the collar  2  is set on the outer periphery of the end portion of the exhaust pipe  1 , and the edge of the outer end of the collar  2  is abutted against the extension portion  1   a  at the edge of the end portion of the exhaust pipe  1 . Then, as shown in FIGS.  4 ( b ) and  4 ( c ), a portion of the collar  2  is crimped in the vertical direction by the crimping means, wherein shown as upper and lower crimping dies  8  and  9 , with a result that the outer peripheries of the exhaust pipe  1  and the portion of the collar  2  are crimped together to be integrated with each other. The collar  2  is thus rigidly fixed to the exhaust pipe  1  by the crimp Ck. It is readily obvious to those of ordinary skill in the art that the crimping means is not limited to the upper and lower crimping dies  8  and  9 . For example, the crimping means may be dies operable to crimp collar  2  at locations around the periphery thereof, not along the entire periphery as shown. Moreover, the position of the dies  8  and  9  are not limited to the width or style shown. Furthermore, the dies  8  and  9  are not limited to the width and position shown in the Figures.  
         [0028]    The structure of mounting the exhaust pipe  1 , on which the collar  2  has been fixed by the crimp Ck as described above, to the exhaust port Pe of the engine E will be described below with reference to FIG. 5. An annular fitting groove  11  is formed in the opening end portion of the exhaust port Pe. The end portion of the exhaust pipe  1 , on which the collar  2  has been fixed by crimping, is fitted in the fitting groove  11 . Two stud bolts  4  are planted by screwing in the opening end portion of the exhaust port Pe. The exhaust pipe  1  is set to the exhaust port Pe such that the two stud bolts  4  are allowed to pass through the bolt holes  5  and fastened with nuts  6 , to thus rigidly hold the collar  2  together with the extension portion  1   a  of the exhaust pipe  1  between the end surface of the exhaust port Pe and the joint  3 . In this way, the exhaust pipe  1  can be integrally connected to the exhaust port Pe of the engine E.  
         [0029]    According to the connection portion structure of the exhaust pipe  1  in the first embodiment, it is possible to rigidly connect the exhaust pipe  1  to the exhaust port Pe without occurrence of any stress concentration therebetween, and to make a clearance between the exhaust pipe  1  and the collar  2  as small as possible. Also since welding beads which appeared in the above described related art structure are not present, the flow resistance of exhaust gas is not increased, and thereby it is not required to perform mechanical treatment for reducing the flow resistance of exhaust gas. Further, since the welding means is not required to implement the present invention, it is possible to significantly reduce the cost of the exhaust structure and the manufacturing cost thereof.  
         [0030]    A second embodiment of the present invention will be described below with reference to FIGS.  6  to  8 .  
         [0031]    [0031]FIG. 6 is a side view, with an essential portion broken away taken along line  6 - 6  of FIG. 7, showing an exhaust pipe including a connection device of the present invention; FIG. 7 is a sectional view taken on line  7 - 7  of FIG. 6; and FIG. 8 is a sectional view showing a state in which the exhaust pipe is assembled in an engine. In these figures, parts corresponding to those in the first embodiment are designated by the same characters.  
         [0032]    In the second embodiment, a positioning means Fi is provided between a collar  102 , fixed at an end portion of the exhaust pipe  1  by crimping, and a joint  103  fitted to the exhaust pipe  1 . A pair of positioning projections  102   a , spaced at a phase difference of approximately 180°, are formed on the inner end surface, to be abutted against the joint  103 , of the cylindrical collar  102  in such a manner as to project therefrom in the axial direction. Meanwhile, a pair of positioning recessed grooves  103   a  corresponding to the pair of positioning projections  102   a , which are similarly spaced at a phase difference of approximately 180°, are formed on the inner peripheral surface of the joint  103  formed into a rhombic shape and having a pair of bolt holes  105  in such a manner as to be each located at an intermediate portion between the pair of bolt holes  105 . The projections  102   a  and the recessed grooves  103   a  constitute the positioning means Fi. It is readily apparent to those of ordinary skill in the art that the positioning means Fi is not limited to the projection pairs  102   a  and the recessed grooves  103   a . For example , the positioning means Fi may be any means capable of aligning the exhaust pipe  1  with the exhaust port Pe.  
         [0033]    Like the first embodiment, the collar  102  is fixed using a crimp Ck on the outer periphery of the end portion, on the connection side to the exhaust pipe Pe, of the exhaust pipe  1 , and the joint  103  is slidably fitted on the outer periphery of the end portion, positioned inwardly from the collar  102 , of the exhaust pipe  1 . The inner end surface of the collar  102  is abutted against one end surface of the joint  103 . At this time, the peripheral positioning between the collar  102  and the joint  103  is performed by fitting the pair of projections  102   a  of the collar  102  in the pair of the recessed grooves  103   a  of the joint  103 .  
         [0034]    The pair of bolt holes  105  of the joint  103  are allowed to pass through the stud bolts  4  planted by screwing in an opening end surface of the exhaust port Pe, and the stud bolts  4  are screwed with nuts  6 . In this way, the collar  102  is forcibly held between the end surface of the exhaust port Pe and the joint  103 , so that the exhaust pipe  1  is integrally connected to the exhaust port Pe.  
         [0035]    According to the second embodiment, in addition to the same function and effect as those of the first embodiment, the peripheral positioning between the collar  102  and the joint  103  can be simply performed by the positioning means Fi, with a result that the exhaust pipe  1  is easily connected to the exhaust port Pe.  
         [0036]    A third embodiment of the present invention will be described with reference to FIG. 9.  
         [0037]    [0037]FIG. 9 is a sectional view showing a state in which an exhaust pipe is assembled in the engine. In the Figure, parts corresponding to those described in the first and second embodiments are designated by the same characters.  
         [0038]    The third embodiment is characterized by additionally providing a reinforcing outer pipe  20  on the exhaust pipe  1 . A cylindrical outer pipe  20  having a specific length is fitted on a connection side end portion, to be connected to the exhaust port Pe side of the engine E, of the exhaust pipe  1 . A collar  2  is fitted on the outer periphery of the outer pipe  20 . The inner peripheral surface of the collar  2  is fixed to both of the edges of the end portions of the exhaust pipe  1  and the outer pipe  20  by a fixing means  21  such as welding. Alternatively, the fixing means may be bonding using an epoxy, or the collar  2  and the reinforcing outer pipe  20  may be formed integrally together.  
         [0039]    A portion, positioned inwardly from the collar  2 , of the outer pipe  20  is fixed, using a crimp Ck, on the exhaust pipe  1 . To be more specific, like the first embodiment, the entire periphery of the outer pipe  20  is crimped on the entire periphery of a portion of the exhaust pipe  1  in the vertical direction by means dies  8  and  9 . Therefore, the entire peripheries of the outer pipe  20  and the portion the exhaust pipe  1  are crimped together. In this way, the outer pipe  20  is fixed on the exhaust pipe  1  by crimping.  
         [0040]    The joint  3  is slidably fitted on the outer periphery of the outer pipe  20 , and one end of the joint  3  is abutted against the inner surface of the collar  2 .  
         [0041]    Like the first embodiment, the exhaust pipe  1  is integrally connected to the opening end of the exhaust port Pe by means of stud bolts  4  and nuts  6  while holding the collar  2  between the opening end of the exhaust port Pe and the joint  3 .  
         [0042]    In the second embodiment, since the reinforcing outer pipe  20  can be rigidly fixed to the exhaust pipe  1  without use of welding, that is, by crimping, it is possible to significantly increase the strength of the connection portion of the exhaust pipe  1 , and to make a clearance between the exhaust pipe  1  and the outer pipe  20  as small as possible.  
         [0043]    While the first, second and third embodiments of the present invention have been described, such description is for illustrative purpose only, and it is to be understood that many variations may be made without departing from the scope of the present invention. For example, although the entire periphery of the collar or the outer pipe is crimped to the exhaust pipe in the above described embodiments, part of the collar or the outer pipe may be crimped to the exhaust pipe as an alternative.  
         [0044]    While the collar or outer pipe is crimped from outside to the exhaust pipe in the above described embodiments, the exhaust pipe may be crimped from inside, that is, from the inner side of the exhaust pipe, to the collar or the outer pipe.  
         [0045]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.