Method of connecting two elongated portions of metallic plate, method of manufacturing exhaust pipe of two-passage construction, and exhaust pipe of two-passage construction

Abstract

In manufacturing an exhaust pipe of two-passage construction, a metallic plate having a first end and a second end respectively elongated in a longitudinal direction of the exhaust pipe is prepared. The metallic plate is bent into a substantially S shape in cross section. It has a diametrically extending central partition plate and a substantially semicircular peripheral wall on each lateral side of said partition plate in such a manner that a groove of substantially V shape in cross section having a substantially closed end on a radially inner side and an open end on a radially outer side is formed at each diametrically outer portion of the partition plate. A target is provided so as to elongate along the groove in a manner to extend substantially radially outward from the closed end. A welding arc is generated between the target and a welding gun disposed on a side of the open end such that the substantially closed end and the target are welded together.

What is claimed is:  
     
         1 . A method of connecting two elongated portions of a metallic plate, comprising the steps of: 
 longitudinally disposing said two elongated portions at an angle so as to form a groove of substantially V shape in cross section having a substantially closed end and an open end;    providing a target elongated along said groove, said target extending from said substantially closed end toward said open end; and    generating a welding arc between said target and a welding gun disposed on a side of said open end above said target such that said substantially closed end of said two elongated portions and said target are welded together.    
     
     
         2 . The method according to  claim 1 , wherein said target is formed by bending that end of one of said elongated portions which lies on said substantially closed end toward said open end.  
     
     
         3 . The method according to  claim 2 , wherein said target lies on an inner surface of the other of said elongated portions.  
     
     
         4 . The method according to  claim 1 , wherein said target is formed by an independent target other than said elongated members.  
     
     
         5 . A method of manufacturing an exhaust pipe of two-passage construction, comprising the steps of: 
 preparing a metallic plate having a first end and a second end respectively elongated in a longitudinal direction of the exhaust pipe;    bending the metallic plate into a substantially S shape in cross section having a diametrically extending central partition plate and a substantially semicircular peripheral wall on each lateral side of said partition plate in such a manner that a groove of substantially V shape in cross section having a substantially closed end on a radially inner side and an open end on a radially outer side is formed at each diametrically outer portion of said partition plate;    providing a target elongated along said groove in a manner to extend substantially radially outward from said closed end; and    generating a welding arc between said target and a welding gun disposed on a side of said open end such that said substantially closed end and said target are welded together.    
     
     
         6 . The method according to  claim 5 , wherein said target is formed by bending the first end and the second end, respectively, of said metallic plate toward the diametrically outer end of said partition plate.  
     
     
         7 . The method according to  claim 5 , wherein said target is formed by doubly folding a radially outer portion of said partition plate substantially into a U shape, a closed end of said U shape facing radially outward in said groove.  
     
     
         8 . The method according to  claim 6 , wherein said target is formed by providing an independent member other than said metallic plate.  
     
     
         9 . The method according to  claim 5 , wherein said target lies on an inner surface, in said groove, of said partition plate.  
     
     
         10 . A method of manufacturing an exhaust pipe of two-passage construction, comprising the steps of: 
 a) bending two longitudinally elongated metallic plates respectively into substantially semicircles with longitudinally elongated sides being further bent radially inward to thereby form inwardly inclined end portions;    b) assembling the semicircles obtained in step a) together such that said inclined end portions of one semicircle face corresponding inclined end portions of the other semicircle to thereby form a substantially circular semi-product, said semi-product having on each diametrically opposite sides thereof a groove of substantially V shape in cross section with a substantially closed end on a radially inner side and an open end on a radially outer side;    c) interposing a diametrically extending central partition plate along said grooves in a manner to extend diametrically outward from said closed ends, whereby a target is formed by a portion extended beyond each of said closed ends; and    d) generating a welding arc between said target and a welding gun disposed on a side of said open end such that said substantially closed end and said target are welded together.    
     
     
         11 . An exhaust pipe of two-passage construction comprising: 
 a central partition plate extending in a diametrical direction and in a longitudinal direction throughout the exhaust pipe;    a substantially semicircular peripheral wall on each lateral side of said partition plate so as to extend in the longitudinal direction of said partition plate, said partition plate and each of said peripheral walls jointly forming at each of radially outer portions of said partition plate a groove of substantially V shape in cross section having a substantially closed end on a radially inner side and an open end on the radially outer side; and    a target elongated along said groove in a manner to extend substantially radially outward from said substantially closed end of said groove, said target being adapted to be integrally welded with the radially inner side of said groove.    
     
     
         12 . The exhaust pipe of two-passage construction according to  claim 11 , wherein said central partition plate and said semicircular walls are formed by one metallic plate and wherein said target is formed by bending each end of said semicircular walls.  
     
     
         13 . The exhaust pipe of two-passage construction according to  claim 11 , wherein said target is formed by doubly folding a diametrically outer portion of said partition plate substantially into a U shape, a closed end of said U shape facing radially outward in said groove.  
     
     
         14 . The exhaust pipe of two-passage construction according to  claim 11 , wherein said target is formed by providing an independent target member other than said partition plate and said semicircular wall.  
     
     
         15 . The exhaust pipe of two-passage construction according to  claim 12 , wherein said target lies along an inner surface, in said groove, of said partition plate.  
     
     
         16 . The exhaust pipe of two-passage construction according to  claim 11 , wherein said central partition plate and said semicircular walls are formed by independent members and wherein said target is constituted by extending said central partition plate beyond said closed diametrically inner end of said groove.  
     
     
         17 . An exhaust pipe of two-passage construction comprising: 
 a central partition plate extending in a diametrical direction and in a longitudinal direction throughout the exhaust pipe;    a substantially semicircular wall formed on each lateral side of said partition plate so as to extend in the longitudinal direction of said partition plate; and    a groove of substantially V shape in cross section formed on each diametrically outer end portion of said partition plate, said groove having a welded portion between said partition plate and a diametrically inner end of said groove,    wherein said welded portion lies radially inward of an imaginary line of an inner circumference of said semicircular wall.    
     
     
         18 . The exhaust pipe of two-passage construction according to  claim 17 , wherein said partition plate has a larger bending rigidity at a central portion thereof than at both radially outer portions thereof.  
     
     
         19 . The exhaust pipe of two-passage construction according to  claim 17 , wherein said partition plate and said semicircular walls are formed by a single piece of metallic plate.  
     
     
         20 . The exhaust pipe of two-passage construction according to  claim 18 , wherein said partition plate has a larger thickness than the remaining portion of said exhaust pipe.  
     
     
         21 . The exhaust pipe of two-passage construction according to  claim 18 , wherein said partition plate has a plurality of reinforcing ribs elongated in the diametrical direction of said partition plate, said reinforcing ribs being disposed at a longitudinal distance from each other.  
     
     
         22 . The exhaust pipe of two-passage construction according to any one of claims  17  through  21 , wherein said groove of substantially V shape satisfies a condition of j/W<2, wherein j is a depth from a diametrically outer end of said groove to a connecting portion and W is a maximum width of said groove.  
     
     
         23 . The exhaust pipe of two-passage construction according to any one of claims  17  through  21 , wherein said groove of substantially V shape satisfies a condition of L/D≧0.05, wherein D is an imaginary inner diameter of the exhaust pipe and L is a distance from D to a connecting portion.  
     
     
         24 . The exhaust pipe of two-passage construction according to any one of claims  17  through  21 , wherein said groove is formed by a combination of a curved outer portion and a relatively straight portion which follows said curved portion toward diametrically inner end of said groove.