Dual wall exhaust manifold and method of making same

Abstract

The present invention provides an improved dual-wall exhaust manifold assembly. The assembly has inner shells welded together and welded to an inlet flange. Outer shells are inserted into a counterbore of the inlet flange. An outlet flange is slid over the inner shell. The inner shell and the outer shell are inserted into the counterbore of the outlet flange. The outer shells are welded together and to the outlet and inlet flanges. The inlet counterbore and the outlet flange counterbore separate the inner and outer shells.

1 . A dual wall exhaust manifold comprising: 
 an inner shell having a plurality of runners for transporting exhaust gases of an engine, each of the runners having a passageway for transporting the exhaust gases from an inlet to an outlet of the inner shell;    an outer shell substantially enclosing the inner shell, the outer shell spaced apart from the inner shell;    an outlet flange connected to the outlet of the runners, the outlet flange having a bore formed therethrough; and    a counterbore formed in the outlet flange for spacing apart the inner shell and the outer shell, wherein the outer shell is welded to the outlet flange.    
     
     
         2 . The dual wall exhaust manifold of  claim 1  further comprising: 
 an inlet flange welded to the inlet of one of the runners, wherein the inner shell and the outer shell are welded to the inlet flange.    
     
     
         3 . The dual wall exhaust manifold of  claim 2  further comprising: 
 a counterbore formed in the inlet flange, the counterbore positioning the outer shell apart from the inner shell.    
     
     
         4 . The dual wall exhaust manifold of  claim 1  wherein the inner shell is slip fit into the outlet flange, the slit fit allowing for thermal expansion of the inner shell.  
     
     
         5 . The dual wall exhaust manifold of  claim 1  wherein the counterbore of the outlet flange provides a space for welding the outer shell to the outlet flange.  
     
     
         6 . The dual wall exhaust manifold of  claim 1  wherein the inner shell has a first portion and a second portion welded together along overlap areas.  
     
     
         7 . The dual wall exhaust manifold of  claim 1  wherein the outer shell has a first side and a second side welded together, the first side and the second side welded at an overlap joint.  
     
     
         8 . A dual wall exhaust manifold comprising: 
 an inner shell having a plurality of runners formed therein, each runner receiving exhaust gases at an inlet and expelling the gases at an outlet;    an outer shell substantially enclosing the inner shell, the outer shell having a plurality of channels for enclosing the runners;    an inlet flange attached to the inlet of one of the runners, the inlet flange having a bore and a counterbore, the counterbore sized to receive the inner shell and the outer shell wherein the counterbore of the inlet flange positions the outer shell apart from the inner shell to form an air gap between the inner shell and the outer shell.    
     
     
         9 . The dual wall exhaust manifold of  claim 8  wherein the inner shell and the outer shell are welded to the inlet flange.  
     
     
         10 . The dual wall exhaust manifold of  claim 9  wherein the counterbore of the inlet flange has a space for welding the inner shell to the inlet flange.  
     
     
         11 . The dual wall exhaust manifold of  claim 8  wherein the counterbore of the inlet flange has a diameter substantially equal to a diameter of the runner.  
     
     
         12 . The dual wall exhaust manifold of  claim 11  wherein the inner shell is welded to the inlet flange without inhibiting fluid flow from the inner shell through the inlet flange.  
     
     
         13 . The dual wall exhaust manifold of  claim 8  further comprising: 
 an outlet flange attached to the outlet of the runners, the outlet flange having a bore formed therethrough.    
     
     
         14 . The dual wall exhaust manifold of  claim 13  wherein the outlet flange has a counterbore spacing the outer shell apart from the inner shell.  
     
     
         15 . The dual wall exhaust manifold of  claim 14  wherein the outlet flange has a slip fit joint to secure the inner shell, the slip fit joint allowing for thermal expansion of the inner shell.  
     
     
         16 . A dual wall exhaust manifold comprising: 
 an inner shell having a first portion and a second portion welded together, the inner shell having a plurality of runners for transporting exhaust gases of an engine, each of the runners transporting the gases from an inlet to an outlet;    an outer shell having a front side and a rear side welded together, the outer shell substantially surrounding the inner shell;    an inlet flange positioned on the inlet of the runners, wherein the inner shell and the outer shell are welded to the inlet flange; and    an outlet flange positioned on the outlet of the runners, the outlet flange having a slip fit joint for connecting to the inner shell, wherein the outer shell is welded to the outlet flange.    
     
     
         17 . The dual wall exhaust manifold of  claim 16  wherein the first portion and the second portion of the inner shell are welded along an overlap area.  
     
     
         18 . The dual wall exhaust manifold of  claim 17  wherein the inner shell is welded along lip areas located between the runners of the inner shell.  
     
     
         19 . The dual wall exhaust manifold of  claim 16  wherein the front side and the rear side of the outer shell are welded along an overlap joint.  
     
     
         20 . The dual wall exhaust manifold of  claim 16  wherein the weld between the outer shell and the outlet flange extends into the weld of the first portion and the second portion of the inner shell.