EGR cooler

Abstract

The invention relates to an EGR cooler in which cooling water is supplied into and discharged from a shell, exhaust gas being passed through tubes from one of hoods to the other hood for thermal exchange of the exhaust gas with the cooling water. Employed is a structure in which the cooling water is prevented from leaking to flow channels of the exhaust gas, so that engine trouble can be prevented from occurring

1 . An EGR cooler comprising a cylindrical shell, plates fixed to axial opposite ends of said shell so as to close the ends of the shell, hoods fixed to sides of the plates away from said shell so as to enclose end faces of the plates, tubes extending axially within the shell and having opposite ends penetratingly fixed to the respective plates, cooling water being supplied into and discharged from said shell, exhaust gas being passed through said tubes from one of the hoods to the other hood for thermal exchange of said exhaust gas with said cooling water, characterized in that an end of the tube penetrating the plate is formed as a tapered portion with diameter gradually increased toward the side away from the shell, the tapered portion being wholly welded to the plate by laser radiation from the side away from the shell.  
     
     
         2 . An EGR cooler comprising a cylindrical shell, plates fixed to axial opposite ends of said shell so as to close the ends of the shell, hoods fixed to sides of the plates away from said shell so as to enclose end faces of the plates, tubes extending axially within the shell and having opposite ends penetratingly fixed to the respective plates, cooling water being supplied into and discharged from said shell, exhaust gas being passed through said tubes from one of the hoods to the other hood for thermal exchange of said exhaust gas with said cooling water, characterized in that an end of the tube penetrates into a through-hole of the plate which is formed with a notch on the side toward the shell, and is welded to the plate by laser radiation from the side away from the shell such that a laser weld reaches the notch.  
     
     
         3 . An EGR cooler comprising a cylindrical shell, plates fixed to axial opposite ends of said shell so as to close the ends of the shell, hoods fixed to sides of the plates away from said shell so as to enclose end faces of the plates, tubes extending axially within the shell and having opposite ends penetratingly fixed to the respective plates, cooling water being supplied into and discharged from said shell, exhaust gas being passed through said tubes from one of the hoods to the other hood for thermal exchange of said exhaust gas with said cooling water, characterized in that the tubes penetrate into and are fixed to the plate via brazed portions such that an end of the tube extends out from the plate by a predetermined length and the extending end of the tube penetrates into and is fixed to a sub plate by laser weld, whereby said sub plate covers said brazed portions.  
     
     
         4 . An EGR cooler comprising a shell in the form of a cylindrical container, tubes extending axially within the shell and having opposite ends penetratingly fixed to axial opposite ends of said shell, cooling water being supplied into and discharged from said shell, exhaust gas being passed through said tubes for thermal exchange of said exhaust gas with said cooling water, characterized in that the tubes have increased diameter and thickness so as to increase cross sectional areas and strength of flow channels, a gas flange being fitted over tips of the respective tubes extruded out of the shell.