Method of manufacturing exhaust aftertreatment devices

Abstract

The present invention provides improved methods of manufacturing modular exhaust aftertreatment devices. One method in accordance with the present invention includes forming subassemblies each defined by a support mat wrapped around a monolith substrate; determining fracture characteristics of each subassembly, which includes maximum and minimum compressive forces; determining a push-in depth for each subassembly based, in part, on the substrate's dimensions and predetermined gap tolerances of the exhaust aftertreatment devices; soft-stuffing each subassembly into the outer housing according to its respective push-in depth; compressing the outer housing inward to thereby retain the subassemblies within and at least in part by the outer housing, wherein the applied compressive force is between the maximum and minimum compressive forces of the various subassemblies; and sizing the outer housing to eliminate lateral housing growth resulting from compressing the outer housing such that the housing length is substantially equal to a predetermined overall housing length.

1 . A method of assembling an exhaust aftertreatment device including at least one monolith substrate, at least one support mat, and an outer housing, the method comprising:
 forming at least one subassembly at least partially defined by the at least one monolith substrate wrapped in the at least one support mat;   positioning the at least one subassembly inside the outer housing;   securing the at least one subassembly within the outer housing; and   sizing a length of the outer housing such that the housing length is equal to a predetermined overall housing length.   
   
   
       2 . The method of  claim 1 , further comprising:
 determining a push-in depth for the at least one subassembly;   wherein said positioning the at least one subassembly includes pushing the at least one subassembly into the outer housing a distance equal to said push-in depth.   
   
   
       3 . The method of  claim 2 , further comprising:
 determining dimensions of the at least one monolith substrate;   wherein said determining said push-in depth is based at least in part upon said dimensions.   
   
   
       4 . The method of  claim 3 , wherein the exhaust aftertreatment device has an array of predetermined gap tolerances, and wherein said determining said push-in depth is further based at least in part upon said predetermined gap tolerances. 
   
   
       5 . The method of  claim 3 , wherein said dimensions include a length, a width, and dimensional deviations of the at least one monolith substrate. 
   
   
       6 . The method of  claim 1 , wherein said sizing the outer housing length includes reducing an initial housing length via trimming or shearing the outer housing. 
   
   
       7 . The method of  claim 1 , wherein said securing the at least one subassembly includes reducing the outer housing radially inward to thereby compressively retain the at least one subassembly at least in part by pressure from the outer housing. 
   
   
       8 . The method of  claim 7 , further comprising:
 determining a plurality of variable target diameters;   wherein the outer housing is reduced radially inward such that a diameter of the outer housing varies longitudinally in accordance with said plurality of variable target diameters.   
   
   
       9 . The method of  claim 7 , wherein said reducing the outer housing radially inward comprises axially translating the outer housing through a plurality of selectively positionable sizing rolls. 
   
   
       10 . The method of  claim 1 , further comprising:
 determining fracture characteristics of the at least one subassembly, said fracture characteristics including at least a maximum compressive force and a minimum compressive force.   
   
   
       11 . The method of  claim 10 , wherein said reducing the outer housing radially inward comprises axially translating the outer housing through a plurality of selectively positionable sizing rolls, each of said plurality of sizing rolls being configured to selectively apply a variable force to the outer housing that is based at least in part upon said fracture characteristics. 
   
   
       12 . A method of manufacturing modular exhaust aftertreatment devices each having first and second monolith substrates, first and second support mats, and a generally cylindrical outer housing, the method comprising:
 forming a first subassembly defined at least in part by the first monolith substrate wrapped in the first support mat;   forming a second subassembly defined at least in part by the second monolith substrate wrapped in the second support mat;   determining a first push-in depth for the first subassembly and a second push-in depth for the second subassembly;   pushing the first subassembly axially into the outer housing a distance equal to said first push-in depth;   pushing said second subassembly axially into the outer housing a distance equal to said second push-in depth;   reducing the outer housing inward to thereby compressively retain the first and second subassemblies within and at least in part by the outer housing; and   reducing a length of the outer housing such that the housing length is substantially equal to a predetermined overall housing length.   
   
   
       13 . The method of  claim 12 , wherein said reducing the outer housing inward includes axially translating the outer housing through a plurality of positionable sizing rolls spaced circumferentially around an outer periphery of the outer housing. 
   
   
       14 . The method of  claim 13 , further comprising:
 determining first and second fracture characteristics respectively including maximum and minimum compressive forces of the first and second subassemblies;   wherein each of said plurality of sizing rolls is configured to selectively apply a force to the outer housing that is between said maximum and minimum compressive forces of the first and second subassemblies.   
   
   
       15 . The method of  claim 14 , further comprising:
 determining a plurality of variable target diameters based at least in part upon said fracture characteristics;   wherein said plurality of sizing rolls reduces the outer housing radially inward such that a diameter of the outer housing varies longitudinally in accordance with said plurality of variable target diameters.   
   
   
       16 . The method of  claim 12 , wherein said determining said first and second push-in depths is based at least in part upon predetermined inlet-end, outlet-end, and intermonolith gap tolerances of the exhaust aftertreatment devices. 
   
   
       17 . The method of  claim 16 , further comprising:
 determining dimensions for each of the first and second monolith substrates;   wherein said determining said first and second push-in depths is respectively based at least in part upon said dimensions of the first and second monolith substrates.   
   
   
       18 . The method of  claim 17 , wherein the dimensions of each monolith substrate includes a length, width, and dimensional variations of the monolith substrate. 
   
   
       19 . The method of  claim 12 , wherein said reducing the length of the outer housing includes cutting off at least one end portion of the outer housing. 
   
   
       20 . A method of manufacturing a modular exhaust aftertreatment device with predetermined inlet-end, outlet-end, and monolith gap tolerances, the method comprising:
 providing first, second, and third monolith substrates each having a predetermined length, diameter, and dimensional variations;   providing an outer housing having a predetermined overall housing length;   providing first, second, and third support mats;   forming first, second, and third subassemblies respectively defined at least in part by said first, second, and third monolith substrates respectively wrapped in said first, second, and third support mats;   determining fracture characteristics for each of said subassemblies, said fracture characteristics including at least maximum and minimum compressive forces;   determining first, second, and third push-in depths based at least in part upon said predetermined inlet-end, outlet-end, and monolith gap tolerances, and said predetermined first, second, and third lengths, respectively;   pushing said first subassembly axially into said outer housing a distance equal to said first push-in depth;   pushing said second subassembly axially into said outer housing a distance equal to said second push-in depth;   pushing said third subassembly axially into said outer housing a distance equal to said third push-in depth;   determining a plurality of variable target diameters based at least in part upon said fracture characteristics;   compressing said outer housing radially inward via a plurality of selectively positionable sizing rolls to thereby retain said subassemblies within and at least in part by said outer housing, wherein each of said sizing rolls selectively applies a force that is between said maximum and minimum compressive forces of said first, second, and third subassemblies, and wherein said plurality of sizing rolls reduces said outer housing radially inward such that a diameter of the outer housing varies longitudinally in accordance with said plurality of variable target diameters; and   cutting off at least one end portion of the outer housing such that a length of the outer housing is substantially equal to said predetermined overall housing length.