Exhaust constituent sensor and method of packaging the same

Abstract

In an exemplary embodiment, the present invention provides an exhaust constituent sensor comprising a planar sensing element securely held in place within a tubular shield by disposing a high temperature mat support between the tubular inner shield and the planar sensing element. The high temperature mat support comprises suitable mat material, e.g., ceramic fibers or metal mesh, and preferably, comprises silica fibers, alumina fibers, alumina fibers with vermiculite, or any other suitable mat material providing the desired support, strength, and thermal and electrical insulating properties described herein. It is within the scope of the invention that the high temperature mat support may be in the form of a fibrous material or a more rigid preform structure, wherein in both instances, the high temperature mat support is adapted to be disposed concentrically around the planar sensing element for secure packaging thereof.

What is claimed is:  
     
         1 . An exhaust constituent sensor, comprising: 
 a planar sensing element having a first end for connecting with at least one electrical terminal, a second and opposite end for contacting exhaust gas, and a central portion extending therebetween;    a tubular shield within which at least a portion of said planar sensing element extends;    a high temperature mat support disposed between said tubular shield and said planar sensing element and about said central portion of said planar sensing element, wherein said high temperature mat support is selected from the group consisting of fibrous material and mesh material, and wherein said high temperature mat support forms a to an upper portion of said planar sensing element; and    a shell disposed about said tubular shield for mounting said tubular shield to a conduit through which said exhaust gas flows.    
     
     
         2 . The exhaust constituent sensor as set forth in  claim 1  wherein said high temperature mat support is concentrically disposed around at least said central portion of said planar sensing element.  
     
     
         3 . The exhaust constituent sensor as set forth in  claim 1  wherein said high temperature mat support extends between and contacts both said planar sensing element and an inner surface of said tubular shield.  
     
     
         4 . The exhaust constituent sensor as set forth in  claim 1  wherein said high temperature mat support comprises: 
 a ceramic fibrous mat.  
 
     
     
         5 . The exhaust constituent sensor as set forth in  claim 4  wherein said ceramic fibrous mat comprises: 
 alumina fibers, silica fibers, or a mixture thereof.  
 
     
     
         6 . The exhaust constituent sensor as set forth in  claim 1  wherein said high temperature mat support is in the form of a rigid preform, said preform structure having an outer surface for contacting and seating against an inner surface of said tubular shield, and wherein said preform structure includes a central opening through which said planar sensing element passes.  
     
     
         7 . The exhaust constituent sensor as set forth in  claim 6  wherein an inner thermal insulating member is disposed between said preform structure and said planar sensing element, said inner support member being formed of steatite, alumina, or a ceramic material.  
     
     
         8 . The exhaust constituent sensor as set forth in  claim 7  wherein said inner thermal insulating member comprises: 
 a pair of semi-circular ceramic support members, each member having a planar inner surface and an arcuate outer surface, said planar inner surface contacting a planar surface of said planar sensing element and said arcuate outer surface for contacting said preform structure.  
 
     
     
         9 . The exhaust constituent sensor as set forth in  claim 1  further including: 
 an inner thermal insulating member disposed between said high temperature mat support and said planar sensing element, wherein said inner thermal insulating member contacts at least a portion of said planar sensing element.  
 
     
     
         10 . The exhaust constituent sensor as set forth in  claim 9  wherein said inner thermal insulating member comprises a pair of a semi-circular support members disposed on first and second planar surfaces of said planar sensing element.  
     
     
         11 . The exhaust constituent sensor as set forth in  claim 11  wherein said inner thermal insulating member is formed of steatite, alumina, or a ceramic material.  
     
     
         12 . The exhaust sensor as set forth in  claim 1  wherein said high temperature mat support is strengthened by adding a binder or by compressing said high temperature mat support.  
     
     
         13 . The exhaust constituent sensor as set forth in  claim 1  wherein said high temperature mat support comprises a flexible fibrous blanket material.  
     
     
         14 . A method for producing an exhaust constituent sensor, comprising: 
 disposing a high temperature mat support about at least a central portion of a planar sensing element to form a barrier to an upper portion of said planar sensing element, said high temperature mat support securely holding said planar sensing element within said sensor, wherein said high temperature mat support is selected from the group consisting of fibrous material and mesh material, and wherein said planar sensing element having a first end for connection with at least one electrical terminal and an opposite second end for contacting exhaust gas; and    disposing said high temperature mat support and said planar sensing element within a tubular shield within which at least said central portion of said planar sensing element extends.    
     
     
         15 . The method as set forth in  claim 14  further including: 
 wrapping said high temperature mat support around at least said central portion of said planar sensing element, wherein said high temperature mat support comprises a fibrous which contacts at least said central portion of said planar sensing element.  
 
     
     
         16 . The method as set forth in  claim 14  wherein said high temperature mat support and a thermal insulating support member are in the form of a rigid preform structure, wherein said preforming structure includes an opening through which said planar sensing element passes, said preform structure having an outer surface for contacting and seating against an inner surface of said tubular shield when said preform structure is disposed within said tubular shield.  
     
     
         17 . The method as set forth in  claim 16  wherein said thermal insulating support member includes first and second semi-circular thermal insulating members between said high temperature mat support and said planar sensing element, said first and second semi-circular thermal insulating members each including a planar inner surface for seating against said planar sensing element and an outer arcuate surface for seating against an inner arcuate surface of said preform structure.  
     
     
         18 . The method as set forth in  claim 15  further including: 
 disposing an inner thermal insulating member between said planar sensing element and said high temperature mat support.  
 
     
     
         19 . The method as set forth in  claim 18  wherein said thermal insulating support member comprises first and second semi-circular thermal insulating members, said first semi-circular thermal insulating member contacting a first planar surface of said planar sensing element and said second semi-circular thermal insulating member contacting an opposing second planar surface of said planar sensing element.  
     
     
         20 . An exhaust constituent sensor, comprising: 
 a planar sensing element having a first end for connecting with at least one electrical terminal, a second and opposite end for contacting exhaust gas, and a central portion extending therebetween;    a tubular shield within which at least a portion of said planar sensing element extends;    a high temperature mat support disposed between said tubular shield and said planar sensing element and about said central portion of said planar sensing element, wherein said high temperature mat support forms a barrier to an upper portion of said planar sensing element;    a thermal insulating support member disposed between said high temperature mat support and said sensing element; and    a shell disposed about said tubular shield for mounting said tubular shield to a conduit.    
     
     
         21 . The exhaust constituent sensor as set forth in  claim 20 , wherein said thermal insulating support member is in physical contact with said sensing element and said high temperature mat support.  
     
     
         22 . The exhaust constituent sensor as set forth in  claim 21 , wherein said high temperature mat support is in physical contact with said tubular shield.  
     
     
         23 . An exhaust constituent sensor, comprising: 
 a planar sensing element having a first end for connecting with at least one electrical terminal, a second and opposite end for contacting exhaust gas, and a central portion extending therebetween;    a tubular shield within which at least a portion of said planar sensing element extends;    a rigid perform structure comprising a high temperature mat support and a thermal insulating support member, wherein said preform structure includes an opening through which said planar sensing element passes, said preform structure having an outer surface for contacting and seating against an inner surface of said tubular shield, wherein said high temperature mat support is selected from the group consisting of a fibrous material and metal mesh, and wherein said high temperature mat support forms a barrier to an upper portion of said planar sensing element; and    a shell disposed about said tubular shield for mounting said tubular shield to a conduit.    
     
     
         24 . The exhaust constituent sensor as set forth in  claim 23 , wherein said high temperature mat support comprises ceramic fibrous material and vermiculite.